java外文翻译
Java编程语言外文翻译、英汉互译、中英对照
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外文翻译原文及译文学院计算机学院专业计算机科学与技术班级学号姓名指导教师负责教师Java(programming language)Java is a general-purpose, concurrent, class-based, object-oriented computer program- -ming language that is specifically designed to have as few implementation dependencies as possible. It is intended to let application developers "write once, run anywhere" (WORA), meaning that code that runs on one platform does not need to be recompiled to run on another. Java applications are typically compiled to byte code (class file) that can run on any Java virtual machine(JVM) regardless of computer architecture. Java is, as of 2012, one of the most popular programming languages in use, particularly for client-server web applications, with a reported 10 million users. Java was originally developed by James Gosling at Sun Microsystems (which has since merged into Oracle Corporation) and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++, but it has fewer low-level facilities than either of them.The original and reference implementation Java compilers, virtual machines, and class libraries were developed by Sun from 1991 and first released in 1995. As of May 2007, in compliance with the specifications of the Java Community Process, Sun relicensed most of its Java technologies under the GNU General Public License. Others have also developed alternative implementations of these Sun technologies, such as the GNU Compiler for Java and GNU Classpath.Java is a set of several computer software products and specifications from Sun Microsystems (which has since merged with Oracle Corporation), that together provide a system for developing application software and deploying it in across-platform computing environment. Java is used in a wide variety of computing platforms from embedded devices and mobile phones on the low end, to enterprise servers and supercomputers on the high end. While less common, Java appletsare sometimes used to provide improved and secure functions while browsing the World Wide Web on desktop computers.Writing in the Java programming language is the primary way to produce code that will be deployed as Java bytecode. There are, however, byte code compilers available forother languages such as Ada, JavaScript, Python, and Ruby. Several new languages have been designed to run natively on the Java Virtual Machine (JVM), such as Scala, Clojure and Groovy.Java syntax borrows heavily from C and C++, but object-oriented features are modeled after Smalltalk and Objective-C. Java eliminates certain low-level constructs such as pointers and has a very simple memory model where every object is allocated on the heap and all variables of object types are references. Memory management is handled through integrated automatic garbage collection performed by the JVM.An edition of the Java platform is the name for a bundle of related programs from Sun that allow for developing and running programs written in the Java programming language. The platform is not specific to any one processor or operating system, but rather an execution engine (called a virtual machine) and a compiler with a set of libraries that are implemented for various hardware and operating systems so that Java programs can run identically on all of them. The Java platform consists of several programs, each of which provides a portion of its overall capabilities. For example, the Java compiler, which converts Java source code into Java byte code (an intermediate language for the JVM), is provided as part of the Java Development Kit (JDK). The Java Runtime Environment(JRE), complementing the JVM with a just-in-time (JIT) compiler, converts intermediate byte code into native machine code on the fly. An extensive set of libraries are also part of the Java platform.The essential components in the platform are the Java language compiler, the libraries, and the runtime environment in which Java intermediate byte code "executes" according to the rules laid out in the virtual machine specification.In most modern operating systems (OSs), a large body of reusable code is provided to simplify the programmer's job. This code is typically provided as a set of dynamically loadable libraries that applications can call at runtime. Because the Java platform is not dependent on any specific operating system, applications cannot rely on any of the pre-existing OS libraries. Instead, the Java platform provides a comprehensive set of its own standard class libraries containing much of the same reusable functions commonly found in modern operating systems. Most of the system library is also written in Java. For instance, Swing library paints the user interface and handles the events itself, eliminatingmany subtle differences between how different platforms handle even similar components.The Java class libraries serve three purposes within the Java platform. First, like other standard code libraries, the Java libraries provide the programmer a well-known set of functions to perform common tasks, such as maintaining lists of items or performing complex string parsing. Second, the class libraries provide an abstract interface to tasks that would normally depend heavily on the hardware and operating system. Tasks such as network access and file access are often heavily intertwined with the distinctive implementations of each platform. The and java.io libraries implement an abstraction layer in native OS code, then provide a standard interface for the Java applications to perform those tasks. Finally, when some underlying platform does not support all of the features a Java application expects, the class libraries work to gracefully handle the absent components, either by emulation to provide a substitute, or at least by providing a consistent way to check for the presence of a specific feature.The success of Java and its write once, run anywhere concept has led to other similar efforts, notably the .NET Framework, appearing since 2002, which incorporates many of the successful aspects of Java. .NET in its complete form (Microsoft's implementation) is currently only fully available on Windows platforms, whereas Java is fully available on many platforms. .NET was built from the ground-up to support multiple programming languages, while the Java platform was initially built to support only the Java language, although many other languages have been made for JVM since..NET includes a Java-like language called Visual J# (formerly named J++) that is incompatible with the Java specification, and the associated class library mostly dates to the old JDK 1.1 version of the language. For these reasons, it is more a transitional language to switch from Java to the .NET platform, than a first class .NET language. Visual J# was discontinued with the release of Microsoft Visual Studio 2008. The existing version shipping with Visual Studio 2005will be supported until 2015 as per the product life-cycle strategy.In June and July 1994, after three days of brainstorming with John Gage, the Director of Science for Sun, Gosling, Joy, Naughton, Wayne Rosing, and Eric Schmidt, the team re-targeted the platform for the World Wide Web. They felt that with the advent of graphical web browsers like Mosaic, the Internet was on its way to evolving into the samehighly interactive medium that they had envisioned for cable TV. As a prototype, Naughton wrote a small browser, Web Runner (named after the movie Blade Runner), later renamed Hot Java.That year, the language was renamed Java after a trademark search revealed that Oak was used by Oak Technology. Although Java 1.0a was available for download in 1994, the first public release of Java was 1.0a2 with the Hot Java browser on May 23, 1995, announced by Gage at the Sun World conference. His announcement was accompanied by a surprise announcement by Marc Andreessen, Executive Vice President of Netscape Communications Corporation, that Netscape browsers would be including Java support. On January 9, 1996, the Java Soft group was formed by Sun Microsystems to develop the technology.Java编程语言Java是一种通用的，并发的，基于类的并且是面向对象的计算机编程语言，它是为实现尽可能地减少执行的依赖关系而特别设计的。
java英汉互译
java英汉互译Java是一种广泛使用的编程语言，它是一种面向对象的语言，最初由Sun Microsystems开发。
Java的设计目标是让开发者编写一次代码，然后可以在不同的平台上运行，这种特性被称为“一次编写，到处运行”。
Java的语法与C++类似，但是Java具有更强的安全性和可移植性。
Java的英汉互译是Java English-Chinese Translation，它是指将Java程序中的英文单词翻译成中文，或将中文翻译成英文。
Java英汉互译在软件开发中非常重要，因为Java程序中的注释、变量名、方法名等都需要进行翻译，以便程序员能够更好地理解和维护代码。
Java英汉互译的实现方式有多种，其中最常用的是使用翻译工具或翻译软件。
这些工具可以自动将Java程序中的英文单词翻译成中文，或将中文翻译成英文。
翻译工具的优点是速度快、准确度高，但是由于语言的复杂性，翻译工具有时会出现错误或不准确的翻译结果。
除了翻译工具，Java程序员还可以使用在线翻译网站或翻译软件进行英汉互译。
这些工具可以帮助程序员快速翻译Java程序中的英文单词，但是需要注意的是，翻译结果需要进行人工校对，以确保翻译的准确性和可读性。
在进行Java英汉互译时，程序员需要注意以下几点：1. 翻译结果需要符合语法规范，以便程序能够正常运行。
2. 翻译结果需要准确无误，以避免程序出现错误或漏洞。
3. 翻译结果需要易于理解和维护，以便程序员能够快速定位和修复问题。
总之，Java英汉互译是Java程序员必备的技能之一，它可以帮助程序员更好地理解和维护代码，提高程序的可读性和可维护性。
在进行翻译时，程序员需要注意翻译结果的准确性和可读性，以确保程序的正常运行和稳定性。
JAVA外文资料翻译
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外文文献原文及翻译 作 者：辛明 生物医学工程学院影像工程专业 生物医学工程学院信息技术系 指导老师：杨谊
Parsing Java Abstraction of the Difference Between Classes and Interfaces In Java language, abstract scale-up and with support class abstraction definition of two mechanisms. Because of these two kinds of mechanism of existence, just gives Java powerful object-oriented skills. Abstract scale-up and with between class abstraction definition for support has great similarities, even interchangeable, so many developers into line nonabstract class definition for abstract scale-up and it is becoming more casual with choice. In fact, both between still has the very big difference, for their choice even reflected in problem domain essence of understanding, to design the intentions of the understand correctly and reasonable. This paper will for the difference analysis, trying to give a developer with a choice between them are based. Understand class abstraction Abstract class and interface in Java language is used for abstract classes (in this article nonabstract class not from abstract scale-up translation, it represents an abstract body, and abstract scale-up for Java language used to define class abstraction in one way, please readers distinguish) defined, then what are the abstract classes, use abstract classes for us any good? In object-oriented concept, we know all objects is through class to describe, but in turn not such. Not all classes are used to describe object, if a class does not contain enough information to portray a concrete object, this class is abstract classes. Abstract classes are often used to characterization of problem field in our analysis, design that the abstract concepts, is to the series will look different, but essentially the same exact conception of abstraction. For example: if we carry out a graphical editing software development, will find problem domain exists round, triangle so some specific concept, they are different, but they all belong to shape such a concept, shape this concept in problem domain is not exist, it is an abstract concept. Precisely because the abstract concepts in problem field no corresponding specific concept, so to characterization abstract concepts nonabstract class cannot be instantiated. In an object-oriented field, mainly used for class abstraction types hidden. We can construct a fixed a group of behavior of abstract description, but this group of behavior but can have any a possible concrete implementation. This abstract describe is abstract classes, and this an arbitrary a possible concrete realization is behaved for all possible derived class. Modules can be operating an abstract body. Due to the module dependent on a fixed abstraction body, so it can are not allowed to modify, Meanwhile, through the abstract derived from the body, also can expand the behavior of this module function. Familiar with OCP readers must know, object-oriented design to be able to achieve a core principles OCP (Open - Closed flying), class abstraction is one of the key. From the perspectives of grammar definition abstract class and interface
JAVA外文文献+翻译
Java and the InternetIf Java is, in fact, yet another computer programming language, you may question why it is so important and why it is being promoted as a revolutionary step in computer programming. The answer isn’t immediately obvious if you’re coming from a traditional programming perspective. Although Java is very useful for solving traditional stand-alone programming problems, it is also important because it will solve programming problems on the World Wide Web.1.Client-side programmingThe Web’s initial server-browser design provided for interactive content, but the interactivity was completely provided by the server. The server produced static pages for the client browser, which would simply interpret and display them. Basic HTML contains simple mechanisms for data gathering: text-entry boxes, check boxes, radio boxes, lists and drop-down lists, as well as a button that can only be programmed to reset the data on the form or “submit” the data on the form back to the server. This submission passes through the Common Gateway Interface (CGI) provided on all Web servers. The text within the submission tells CGI what to do with it. The most common action is to run a program located on the server in a directory that’s typically called “cgi-bin.” (If you watch the address window at the top of your browser when you push a button on a Web page, you can sometimes see “cgi-bin” within all the gobbledygook there.) These programs can be written in most languages. Perl is acommon choice because it is designed for text manipulation and is interpreted, so it can be installed on any server regardless of processor or operating system. Many powerful Web sites today are built strictly on CGI, and you can in fact do nearly anything with it. However, Web sites built on CGI programs can rapidly become overly complicated to maintain, and there is also the problem of response time. The response of a CGI program depends on how much data must be sent, as well as the load on both the server and the Internet. (On top of this, starting a CGI program tends to be slow.) The initial designers of the Web did not foresee how rapidly this bandwidth would be exhausted for the kinds of applications people developed. For example, any sort of dynamic graphing is nearly impossible to perform with consistency because a GIF file must be created and moved from the server to the client for each version of the graph. And you’ve no doubt had direct experience with something as simple as validating the data on an input form. You press the submit button on a page; the data is shipped back to the server; the server starts a CGI program that discovers an error, formats an HTML page informing you of the error, and then sends the page back to you; you must then back up a page and try again. Not only is this slow, it’s inelegant.The solution is client-side programming. Most machines that run Web browsers are powerful engines capable of doing vast work, and with the original static HTML approach they are sitting there, just idly waiting for the server to dish up the next page. Client-side programming means that the Web browser is harnessed to do whatever work it can, and the result for the user is a much speedier and more interactive experience at your Web site.The problem with discussions of client-side programming is that they aren’t very different from discussions of programming in general. The parameters are almost the same, but the platform is different: a Web browser is like a limited operating system. In the end, you must still program, and this accounts for the dizzying array of problems and solutions produced by client-side programming. The rest of this section provides an overview of the issues and approaches in client-side programming.2.Plug-insOne of the most significant steps forward in client-side programming is the development of the plug-in. This is a way for a programmer to add new functionality to the browser by downloading a piece of code that plugs itself into the appropriate spot in the browser. It tells the browser “from now on you can perform this new activity.” (You ne ed to download the plug-in only once.) Some fast and powerful behavior is added to browsers via plug-ins, but writing a plug-in is not a trivial task, and isn’t something you’d want to do as part of the process of building a particular site. The value of the plug-in for client-side programming is that it allows an expert programmer to develop a new language and add that language to a browser without the permission of the browser manufacturer. Thus, plug-ins provide a “back door” that allows the creation of new client-side programming languages (although not all languages are implemented as plug-ins).3.Scripting languagesPlug-ins resulted in an explosion of scripting languages. With a scripting language you embed the source code for your client-side program directly into the HTML page, and the plug-in that interprets that language is automatically activated while the HTML page is being displayed. Scripting languages tend to be reasonably easy to understand and, because they are simply text that is part of an HTML page, they load very quickly as part of the single server hit required to procure that page. The trade-off is that your code is exposed for everyone to see (and steal). Generally, however, you aren’t doing amazingly sophisticated things with scripting languages so this is not too much of a hardship.This points out that the scripting languages used inside Web browsers are really intended to solve specific types of problems, primarily the creation of richer and more interactive graphical user interfaces (GUIs). However, a scripting language might solve 80 percent of the problems encountered in client-side programming. Your problems might very well fit completely withinthat 80 percent, and since scripting languages can allow easier and faster development, you should probably consider a scripting language before looking at a more involved solution such as Java or ActiveX programming.The most commonly discussed browser scripting languages are JavaScript (which has nothing to do with Java; it’s named that way just to grab some of Java’s marketing momentum), VBScript (which looks like Visual Basic), and Tcl/Tk, which comes from the popular cross-platform GUI-building language. There are others out there, and no doubt more in development.JavaScript is probably the most commonly supported. It comes built into both Netscape Navigator and the Microsoft Internet Explorer (IE). In addition, there are probably more JavaScript books available than there are for the other browser languages, and some tools automatically create pages using JavaScript. However, if you’re already fluent in Visual Basic or Tcl/Tk, you’ll be more productive using those scripting languages rather than learning a new one. (You’ll have your hands full dealing with the Web issues already.)4.JavaIf a scripting language can solve 80 percent of the client-side programming problems, what about the other 20 percent—the “really hard stuff?” The most popular solution today is Java. Not only is it a powerful programming language built to be secure, cross-platform, and international, but Java is being continually extended to provide language features and libraries that elegantly handle problems that are difficult in traditional programming languages, such as multithreading, database access, network programming, and distributed computing. Java allows client-side programming via the applet.An applet is a mini-program that will run only under a Web browser. The applet is downloaded automatically as part of a Web page (just as, for example, a graphic is automatically downloaded). When the applet is activated it executes a program. This is part of its beauty—it provides you with a way to automatically distribute the client software from the server at the time the user needs the client software, and no sooner. The user gets the latest version of the client software without fail and without difficult reinstallation. Because of theway Java is designed, the programmer needs to create only a single program, and that program automatically works with all computers that have browsers with built-in Java interpreters. (This safely includes the vast majority of machines.) Since Java is a full-fledged programming language, you can do as much work as possible on the client before and after making requests of the server. F or example, you won’t need to send a request form across the Internet to discover that you’ve gotten a date or some other parameter wrong, and your client computer can quickly do the work of plotting data instead of waiting for the server to make a plot and ship a graphic image back to you. Not only do you get the immediate win of speed and responsiveness, but the general network traffic and load on servers can be reduced, preventing the entire Internet from slowing down.One advantage a Java applet has ove r a scripted program is that it’s in compiled form, so the source code isn’t available to the client. On the other hand, a Java applet can be decompiled without too much trouble, but hiding your code is often not an important issue. Two other factors can be important. As you will see later in this book, a compiled Java applet can comprise many modules and take multiple server “hits” (accesses) to download. (In Java 1.1 and higher this is minimized by Java archives, called JAR files, that allow all the required modules to be packaged together and compressed for a single download.) A scripted program will just be integrated into the Web page as part of its text (and will generally be smaller and reduce server hits). This could be important to the responsiveness of your Web site. Another factor is the all-important learning curve. Regardless of what you’ve heard, Java is not a trivial language to learn. If you’re a Visual Basic programmer, moving to VBScript will be your fastest solution, and since it will probably solve most typical client/server problems you might be hard pressed to justify learning Java. If you’re experienced with a scripting language you will certainly benefit from looking at JavaScript or VBScript before committing to Java, since they might fit your needs handily and you’ll be more productive sooner.to run its applets withi5.ActiveXTo some degree, the competitor to Java is Microsoft’s ActiveX, although it takes a completely different approach. ActiveX was originally a Windows-only solution, although it is now being developed via an independent consortium to become cross-platform. Effectively, ActiveX says “if your program connects to its environment just so, it can be dropped into a Web page and run under a browser that supports ActiveX.” (I E directly supports ActiveX and Netscape does so using a plug-in.) Thus, ActiveX does not constrain you to a particular language. If, for example, you’re already an experienced Windows programmer using a language such as C++, Visual Basic, or Borland’s Del phi, you can create ActiveX components with almost no changes to your programming knowledge. ActiveX also provides a path for the use of legacy code in your Web pages.6.SecurityAutomatically downloading and running programs across the Internet can sound like a virus-builder’s dream. ActiveX especially brings up the thorny issue of security in client-side programming. If you click on a Web site, you might automatically download any number of things along with the HTML page: GIF files, script code, compiled Java code, and ActiveX components. Some of these are benign; GIF files can’t do any harm, and scripting languages are generally limited in what they can do. Java was also designed to run its applets within a “sandbox” of safety, which prevents it from wri ting to disk or accessing memory outside the sandbox.ActiveX is at the opposite end of the spectrum. Programming with ActiveX is like programming Windows—you can do anything you want. So if you click on a page that downloads an ActiveX component, that component might cause damage to the files on your disk. Of course, programs that you load onto your computer that are not restricted to running inside a Web browser can do the same thing. Viruses downloaded from Bulletin-Board Systems (BBSs) have long been a problem, but the speed of the Internet amplifies the difficulty.The solution seems to be “digital signatures,” whereby code is verified to show who the author is. This is based on the idea that a virus works because its creator can be anonymous, so if you remove the anonymity individuals will be forced to be responsible for their actions. This seems like a good plan because it allows programs to be much more functional, and I suspect it will eliminate malicious mischief. If, however, a program has an unintentional destructive bug it will still cause problems.The Java approach is to prevent these problems from occurring, via the sandbox. The Java interpreter that lives on your local Web browser examines the applet for any untoward instructions as the applet is being loaded. In particular, the applet cannot write files to disk or erase files (one of the mainstays of viruses). Applets are generally considered to be safe, and since this is essential for reliable client/server systems, any bugs in the Java language that allow viruses are rapidly repaired. (It’s worth noting that the browser software actually enforces these security restrictions, and some browsers allow you to select different security levels to provide varying degrees of access to your system.) You might be skeptical of this rather draconian restriction against writing files to your local disk. For example, you may want to build a local database or save data for later use offline. The initial vision seemed to be that eventually everyone would get online to do anything important, but that was soon seen to be impractical (although low-cost “Internet appliances” might someday satisfy the needs of a significant segment of users). The solution is the “signed applet” that uses public-key encryption to verify that an applet does indeed come from where it claims it does. A signed applet can still trash your disk, but the theory is that since you can now hold the applet creator accountable they won’t do vicious things. Java provides a framework for digital signatures so that you will eventually be able to allow an applet to step outside the sandbox if necessary. Digital signatures have missed an important issue, which is the speed that people move around on the Internet. If you download a buggy program and it does something untoward, how long will it be before you discover the damage? It could be days or even weeks. By then, how will you track down the program that’s done it? And what good will it do you at that point?7.Internet vs. intranetThe Web is the most general solution to the client/server problem, so it makes sense that you can use the same technology to solve a subset of the problem, in particular the classic client/server problem within a company. With traditional client/server approaches you have the problem of multiple types of client computers, as well as the difficulty of installing new client software, both of which are handily solved with Web browsers and client-side programming. When Web technology is used for an information network that is restricted to a particular company, it is referred to as an intranet. Intranets provide much greater security than the Internet, since you can physically control access to the servers within your company. In terms of training, it seems that once people und erstand the general concept of a browser it’s much easier for them to deal with differences in the way pages and applets look, so the learning curve for new kinds of systems seems to be reduced.The security problem brings us to one of the divisions that seems to be automatically forming in the world of client-side programming. If your program is running on the Internet, you don’t know what platform it will be working under, and you want to be extra careful that you don’t disseminate buggy code. You need something cross-platform and secure, like a scripting language or Java.If you’re running on an intranet, you might have a different set of constraints. It’s not uncommon that your machines could all be Intel/Windows platforms. On an intranet, you’re respon sible for the quality of your own code and can repair bugs when they’re discovered. In addition, you might already have a body of legacy code that you’ve been using in a more traditional client/server approach, whereby you must physically install client programs every time you do an upgrade. The time wasted in installing upgrades is the most compelling reason to move to browsers, because upgrades are invisible and automatic. If you are involved in such an intranet, the most sensible approach to take is the shortest path that allows you to use your existing code base, rather than trying to recode your programs in a new language.When faced with this bewildering array of solutions to the client-side programming problem, the best plan of attack is a cost-benefit analysis. Consider the constraints of your problem and what would be the shortest path to your solution. Since client-side programming is still programming, it’s always a good idea to take the fastest development approach for your particular situation. This is an aggressive stance to prepare for inevitable encounters with the problems of program development.8.Server-side programmingThis whole discussion has ignored the issue of server-side programming. What happens when you make a request of a server? Most of the time the request is simply “send me this file.” Your browser then interprets the file in some appropriate fashion: as an HTML page, a graphic image, a Java applet, a script program, etc. A more complicated request to a server generally involves a database transaction. A common scenario involves a request for a complex database search, which the server then formats into an HTML page and sends to you as the result. (Of course, if the client has more intelligence via Java or a scripting language, the raw data can be sent and formatted at the client end, which will be faster and less load on the server.) Or you might want to register your name in a database when you join a group or place an order, which will involve changes to that database. These database requests must be processed via some code on the server side, which is generally referred to as server-side programming. Traditionally, server-side programming has been performed using Perl and CGI scripts, but more sophisticated systems have been appearing. These include Java-based Web servers that allow you to perform all your server-side programming in Java by writing what are called servlets. Servlets and their offspring, JSPs, are two of the most compelling reasons that companies who develop Web sites are moving to Java, especially because they eliminate the problems of dealing with differently abled browsers.9. separate arena: applicationsMuch of the brouhaha over Java has been over applets. Java is actually a general-purpose programming language that can solve any type of problem—at least in theory. And as pointed out previously, there might be more effective ways to solve most client/server problems. When you move out of the applet arena (and simultaneously release the restrictions, such as the one against writing to disk) you enter the world of general-purpose applications that run standalone, without a Web browser, just like any ordinary program does. Here, Java’s strength is not only in its portability, but also its programmability. As you’l l see throughout this book, Java has many features that allow you to create robust programs in a shorter period than with previous programming languages. Be aware that this is a mixed blessing. You pay for the improvements through slower execution speed (although there is significant work going on in this area—JDK 1.3, in particular, introduces the so-called “hotspot” performance improvements). Like any language, Java has built-in limitations that might make it inappropriate to solve certain types of programming problems. Java is a rapidly evolving language, however, and as each new release comes out it becomes more and more attractive for solving larger sets of problems.Java和因特网既然Java不过另一种类型的程序设计语言，大家可能会奇怪它为什么值得如此重视，为什么还有这么多的人认为它是计算机程序设计的一个里程碑呢？如果您来自一个传统的程序设计背景，那么答案在刚开始的时候并不是很明显。
Java中英翻译
abstract (关键字) 抽象['.bstr.kt]access vt.访问,存取['.kses]'(n.入口,使用权)algorithm n.算法['.lg.riem]Annotation [java]代码注释[.n.u'tei..n]anonymous adj.匿名的[.'n.nim.s]'(反义：directly adv.直接地,立即[di'rektli, dai'rektli])apply v.应用,适用[.'plai]application n.应用,应用程序[,.pli'kei..n]' (application crash 程序崩溃) arbitrary a.任意的['ɑ:bitr.ri]argument n.参数;争论,论据['ɑ:gjum.nt]'(缩写args)assert (关键字) 断言[.'s.:t] ' (java 1.4 之后成为关键字)associate n.关联(同伴,伙伴) [.'s.u.ieit]attribute n.属性(品质,特征) [.'tribju:t]boolean (关键字) 逻辑的, 布尔型call n.v.调用; 呼叫; [k.:l]circumstance n.事件(环境,状况) ['s.:k.mst.ns]crash n.崩溃,破碎[kr..]cohesion内聚,黏聚,结合[k.u'hi:..n](a class is designed with a single, well-focoused purpose. 应该不止这点) command n. 命令,指令[k.'mɑ:nd](指挥, 控制) (command-line 命令行)Comments [java]文本注释['k.ments]compile [java] v.编译[k.m'pail]' Compilation n.编辑[,k.mpi'lei..n] const (保留字)constant n. 常量, 常数, 恒量['k.nst.nt]continue (关键字)coupling耦合,联结['k.pli.]making sure that classes know about other classes only through their APIs. declare [java]声明[di'kl..]default (关键字) 默认值; 缺省值[di'f.:lt]delimiter定义符; 定界符Encapsulation[java]封装(hiding implementation details)Exception [java]例外; 异常[ik'sep..n]entry n.登录项, 输入项, 条目['entri]enum (关键字)execute vt.执行['eksikju:t]exhibit v.显示, 陈列[ig'zibit]exist存在, 发生[ig'zist] '(SQL关键字exists)extends (关键字) 继承、扩展[ik'stend]false (关键字)final (关键字) finally (关键字)fragments段落; 代码块['fr.gm.nt]FrameWork [java]结构,框架['freimw.:k]Generic [java]泛型[d.i'nerik]goto (保留字) 跳转heap n.堆[hi:p]implements (关键字) 实现['implim.nt]import (关键字) 引入(进口,输入)Info n.信息(information [,inf.'mei..n] )Inheritance [java]继承[in'herit.ns] (遗传,遗产)initialize预置初始化[i'iz]instanceof (关键字) 运算符，用于引用变量，以检查这个对象是否是某种类型。
Java编程思想外文翻译文献
Java编程思想外文翻译文献(文档含中英文对照即英文原文和中文翻译)原文：Thinking in JavaAlthough it is based on C++, Java is more of a “pure” object-oriented language.Both C++ and Java are hybrid languages, but in Java the designers felt that the hybridization was not as important as it was in C++. A hybrid language allows multiple programming styles; the reason C++ is hybrid is to support backward compatibility with the C language. Because C++ is a superset of the C language, it includes many of that language’s undesirable features, which can make some aspects of C++ overly complicated. The Java language assumes that you want to do only object-oriented programming. This means that before you can begin you must shift yourmindset into an object-oriented world (unless it’s already there). The benefit of this initial effort is the ability to program in a language that is simpler to learn and to use than many other OOP languages. In this chapter we’ll see the basic components of a Java program and we’ll lea rn that everything in Java is an object, even a Java program.Each programming language has its own means of manipulating data. Sometimes the programmer must be constantly aware of what type of manipulation is going on. Are you manipulating the object directly, or are you dealing with some kind of indirect representation (a pointer in C or C++) that must be treated with a special syntax?All this is simplified in Java. You treat everything as an object, using a single consistent syntax. Although you treat everything as an object, the identifier you manipulate is actually a “reference” to an object. You might imagine this scene as a television (the object) with your remote control (the reference). As long as you’re holding this reference, you have a connecti on to the television, but when someone says “change the channel” or “lower the volume,” what you’re manipulating is the reference, which in turn modifies the object. If you want to move around the room and still control the television, you take the remote/reference with you, not the television.Also, the remote control can stand on its own, with no television. That is, just because you have a reference doesn’t mean there’s necessarily an object connected to it. So if you want to hold a word or sentence, you create a String reference:But here you’ve created only the reference, not an object. If you decided to send a message to s at this point, you’ll get an error (at run time) because s isn’t actually attached to anything (there’s no television). A safer p ractice, then, is always to initialize a reference when you create it.However, this uses a special Java feature: strings can be initialized with quoted text. Normally, you must use a more general type of initialization for objectsWhen you create a reference, you want to connect it with a new object. You do so, in general, with the new keyword. The keyword new says, “Make me a new one of these objects.” So in the preceding example, you can say:Not only does this mean “Make me a new String,” but it also g ives information about how to make the String by supplying an initial character string.Of course, String is not the only type that exists. Java comes with a plethora of ready-made types. What’s more important is that you can create your own types. In fact, that’s the fundamental activity in Java programming, and it’s what you’ll be learning about in the rest of this bookIt’s useful to visualize some aspects of how things are laid out while the program is running—in particular how memory is arranged. There are six different places to store data: Registers. This is the fastest storage because it exists in a place different from that of other storage: inside the processor. However, the number of registers is severely limited, so registers are allocated by t he compiler according to its needs. You don’t have direct control, nor do you see any evidence in your programs that registers even exist.The stack. This lives in the general random-access memory (RAM) area, but has direct support from the processor via its stack pointer. The stack pointer is moved down to create new memory and moved up to release that memory. This is an extremely fast and efficient way to allocate storage, second only to registers. The Java compiler must know, while it is creating the program, the exact size and lifetime of all the data that is stored on the stack, because it must generate the code to move the stack pointer up and down. This constraint places limits on the flexibility of your programs, so while some Java storage exists on the stack—in particular, object references—Java objects themselves are not placed on the stack.The heap. This is a general-purpose pool of memory (also in the RAM area) where all Java objects live. The nice thing about the heap is that, unlike the stack, the compiler doesn’t need to know how much storage it needs to allocate from the heap or how long that storage must stay on the heap. Thus, there’s a great deal of flexibility in using storage on the heap. Whenever you need to create an object, you simply write the code to create it by using new,and the storage is allocated on the heap when that code is executed. Of course there’s a price you pay for this flexibility. It takes more time to allocate heap storage than it does to allocate stack storage (if you even could create objects on the stack in Java, as you can in C++).Static storage. “Static” is used here in the sense of “in a fixed location” (although it’s also in RAM). Static storage contains data that is available for the entire time a program is running. You can use the static keyword to specify that a particular element of an object is static, but Java objects themselves are never placed in static storage.Constant storage. Constant values are often placed directly in the program code, which is safe since they can never change. Sometimes constants are cordoned off by themselves so that they can be optionally placed in read-only memory (ROM), in embedded systems.Non-RAM storage. If data lives completely outside a program, it can exist while the program is not running, outside the control of the program. The two primary examples of this are streamed objects, in which objects are turned into streams of bytes, generally to be sent to another machine, and persistent objects, in which the objects are placed on disk so they will hold their state even when the program is terminated. The trick with these types of storage is turning theobjects into something that can exist on the other medium, and yet can be resurrected into a regular RAM-based object when necessary. Java provides support for lightweight persistence, and future versions of Java might provide more complete solutions for persistence One group of types, which you’ll use quite often in your programming, gets special treatment. You can think of these as “primitive” types. The reason for the special treatment is that to create an object with new—especially a small, simple variable—isn’t very efficient, because new places objects on the heap. For these types Java falls back on the approach taken by C and C++. That is, instead of creating the variable by using new, an “automatic” variable is created that is not a reference. The variable holds the value, and it’s placed on the stack, so it’s much more efficient.Java determines the size of each p rimitive type. These sizes don’t change from one machine architecture to another as they do in most languages. This size invariance is one reason Java programs are portableAll numeric types are signed, so don’t look for unsigned types.The size of the boolean type is not explicitly specified; it is only defined to be able to take the literal values true or false.The “wrapper” classes for the primitive data types allow you to make a nonprimitive object on the heap to represent that primitive type. For example:char c = 'x';Character C = new Character(c);Or you could also use:Character C = new Character('x');The reasons for doing this will be shown in a later chapter.Java includes two classes for performing high-precision arithmetic: Big Integer and BigDecimal. Although these approximately fit into the same category as the “wrapper” classes, neither one has a primitive analogue.Both classes have methods that provide analogues for the operations that you perform on primitive types. That is, you can do anything with a BigInteger or BigDecimal that you can with an int or float, it’s just that you must use method calls instead of operators. Also, since there’s more involved, the operations will be slower. You’re exchanging speed for accuracy. BigInteger supports arbitrary-precision integers. This means that you can accurately represent integral values of any size without losing any information during operations.BigDecimal is for arbitrary-precision fixed-point numbers; you can use these for accurate monetary calculations, for example.Consult the JDK documentation for details about the constructors and methods you can call for these two classesVirtually all programming languages support arrays. Using arrays in C and C++ is perilous because those arrays are only blocks of memory. If a program accesses the array outside of its memory block or uses the memory before initialization (common programming errors), there will be unpredictable results.One of the primary goals of Java is safety, so many of the problems that plague programmers in C and C++ are not repeated in Java. A Java array is guaranteed to be initialized and cannot be accessed outside of its range. The range checking comes at the price of having a small amount of memory overhead on each array as well as verifying the index at run time, but the assumption is that the safety and increased productivity is worth the expense.When you create an array of objects, you are really creating an array of references, and each of those references is automatically initialized to a special value with its own keyword: null. When Java sees null, it recognizes that the reference in question isn’t pointing to an object. You must assign an object to each reference before you use it, and if you try to use a reference that’s still null,the problem will be reported at run time. Thus, typical array errors are prevented in Java.You can also create an array of primitives. Again, the compiler guarantees initialization because it zeroes the memory for that array.Arrays will be covered in detail in later chapters.In most programming languages, the concept of the lifetime of a variable occupies a significant portion of the programming effort. How long does the variable last? If you are supposed to destroy it, when should you? Confusion over variable lifetimes can lead to a lot of bugs, and this section shows how Java greatly simplifies the issue by doing all the cleanup work for you.Most procedural languages have the concept of scope. This determines both the visibility and lifetime of the names defined within that scope. In C, C++, and Java, scope is determined by the placement of curly braces {}. So for example:{int x = 12;// Only x available{int q = 96;// Both x & q available}// Only x available// q “out of scope”}A variable defined within a scope is available only to the end of that scope.Any text after a ‘//’ to the end of a line is a comment.Indentation makes Java code easier to read. Since Java is a free-form language, the extra spaces, tabs, and carriage returns do not affect the resulting program.Note that you cannot do the following, even though it is legal in C and C++:{int x = 12;{int x = 96; // Illegal}}The compiler will announce that the variable x has already been defined. Thus the C and C++ ability to “hide” a variable in a larger scope is not allowed, because the Java designers thought that it led to confusing programs.Java objects do not have the same lifetimes as primitives. When you create a Java object using new, it hangs around past the end of the scope. Thus if you use:{String s = new String("a string");} // End of scopethe reference s vanishes at the end of the scope. However, the String object that s was pointing to is still occupying memory. In this bit of code, there is no way to access the object, because the only reference to it is out of scope. In later chapters you’ll see how the reference to the object can be passed around and duplicated during the course of a program.It turns out that because objects created with new stay around for as long as you want them, a whole slew ofC++ programming problems simply vanish in Java. The hardest problems seem to occur in C++ because you don’t get any help from t he language in making sure that the objects are available when they’re needed. And more important, in C++ you must make sure that you destroy the objects when you’re done with them.That brings up an interesting question. If Java leaves the objects lying around, what keeps them from filling up memory and halting your program? This is exactly the kind of problem that would occur in C++. This is where a bit of magic happens. Java has a garbage collector, which looks at all the objects that were created with new and figures out which ones are not being referenced anymore. Then it releases the memory for those objects, so the memory can be used for new objects. This means that you never need to worry about reclaiming memory yourself. You simply create objects, and when you no longer need them, they will go away by themselves. This eliminates a certain class of programming problem: the so-called “memory leak,” in which a programmer forgets to release memory.If everything is an object, what determines how a particular class of object looks and behaves?Put another way, what establishes the type of an object? You might expect there to be a keyword called “type,” and that certainly would have made sense. Historically, however, most object-oriented languages have used the keyword class to mean “I’m about to tell you what a new type of object looks like.” The class keyword (which is so common that it will not be bold-faced throughout this book) is followed by the name of the new type. For example:class ATypeName { /* Class body goes here */ }This introduces a new type, although the class body consists only of a comment (the stars and slashes and what is inside, which will be discussed later in this chapter), so there is not too much that you can do with it. However, you can create an object of this type using new: ATypeName a = new ATypeName();But you cannot tell it to do much of anything (that is, you cannot send it any interesting messages) until you define some methods for it.When you define a class (and all you do in Java is define classes, make objects of those classes, and send messages to those objects), you can put two types of elements in your class: fields (sometimes called data members), and methods (sometimes called member functions). A field is an object of any type that you can communicate with via its reference. It can also be one of the primitive types (which isn’t a reference). If it is a reference to an object, you must initialize that reference to connect it to an actual object (using new, as seen earlier) in a special method called a constructor (described fully in Chapter 4).If it is a primitive type, you can initialize it directly at the point of definition in the class. (As you’ll see later, references can also be initialized at the poi nt of definition.) Each object keeps its own storage for its fields; the fields are not shared among objects. Here is an example of a class with some fields:class DataOnly {int i;float f;boolean b;}This class doesn’t do anything, but you can create an object:DataOnly d = new DataOnly();You can assign values to the fields, but you must first know how to refer to a member ofan object. This is accomplished by stating the name of the object reference, followed by a period (dot), followed by the name of the member inside the object:objectReference.memberFor example:d.i = 47;d.f = 1.1f; // ‘f’ after number indicates float constantd.b = false;It is also possible that your object might contain other objects that contain data you’d like to modify. For this, you just keep “connecting the dots.” For example:myPlane.leftTank.capacity = 100;The DataOnly class cannot do much of anything except hold data, because it has no methods. To understand how those work, you must first understand arguments and return values, which will be described shortly.译文：Java编程思想“尽管以C++为基础，但Java是一种更纯粹的面向对象程序设计语言”。
JAVA外文翻译
英文原文:The Java programming language and platform have emerged as major technologies for performing e-business functions. Java programming standards have enabled portability of applications and the reuse of application components across computing platforms. Sun Microsystems' Java Community Process continues to be a strong base for the growth of the Java infrastructure and language standards. This growth of open standards creates new opportunities for designers and developers of applications and services .Applications of JavaJava uses many familiar programming concepts and constructs and allows portability by providing a common interface through an external Java Virtual Machine (JVM). A virtual machine is a self-contained operating environment, created by a software layer that behaves as if it were a separate computer. Benefits of creating virtual machines include better exploitation of powerful computing resources and isolation of applications to prevent cross-corruption and improve security.The JVM allows computing devices with limited processors or memory to handle more advanced applications by calling up software instructions inside the JVM to perform most of the work. This also reduces the size and complexity of Java applications because many of the core functions and processing instructions were built into the JVM. As a result, software developers no longer need to re-create the same application for every operating system. Java also provides security by instructing the application to interact with the virtual machine, which served as a barrier between applications and the core system, effectively protecting systems from malicious code.Among other things, Java is tailor-made for the growing Internet because it makes it easy to develop new, dynamic applications that could make the most of the Internet's power and capabilities. Java is now an open standard, meaning that no single entity controls its development and the tools for writing programs in the language are available to everyone. The power of open standards like Java is the ability to break down barriers and speed up progress.Today, you can find Java technology in networks and devices that range from the Internet and scientific supercomputers to laptops and cell phones, from Wall Street market simulators tohome game players and credit cards. There are over 3 million Java developers and now there are several versions of the code. Most large corporations have in-house Java developers. In addition, the majority of key software vendors use Java in their commercial applications (Lazaridis, 2003).ApplicationsJava on the World Wide WebJava has found a place on some of the most popular websites in the world and the uses of Java continues to grow. Java applications not only provide unique user interfaces, they also help to power the backend of websites. Everybody is probably familiar with eBay and Amazon have been Java pioneers on the World Wide Web.eBayFounded in 1995, eBay enables e-commerce on a local, national and international basis with an array of Web sites.You can find it on eBay, even if you didn't know it existed. On a typical day, more than 100 million items are listed on eBay in tens of thousands of categories. on eBay; the world's largest online marketplace.eBay uses Java almost everywhere. To address some security issues, eBay chose Sun Microsystems' Java System Identity Manager as the platform for revamping its identity management system. The task at hand was to provide identity management for more than 12,000 eBay employees and contractors.Now more than a thousand eBay software developers work daily with Java applications. Java's inherent portability allows eBay to move to new hardware to take advantage of new technology, packaging, or pricing, without having to rewrite Java code.Amazon has created a Web Service application that enables users to browse their product catalog and place orders. uses a Java application that searches the Amazon catalog for books whose subject matches a user-selected topic. The application displays ten books that match the chosen topic, and shows the author name, book title, list price, Amazon discount price, and the cover icon. The user may optionally view one review per displayed title and make a buying decision.Java in Data Warehousing & MiningAlthough many companies currently benefit from data warehousing to support corporatedecision making, new business intelligence approaches continue to emerge that can be powered by Java technology. Applications such as data warehousing, data mining, Enterprise Information Portals and Knowledge Management Systems are able to provide insight into customer retention, purchasing patterns, and even future buying behavior.These applications can not only tell what has happened but why and what may happen given certain business conditions; As a result of this information growth, people at all levels inside the enterprise, as well as suppliers, customers, and others in the value chain, are clamoring for subsets of the vast stores of information to help them make business decisions. While collecting and storing vast amounts of data is one thing, utilizing and deploying that data throughout the organization is another.The technical challenges inherent in integrating disparate data formats, platforms, and applications are significant. However, emerging standards such as the Application Programming Interfaces that comprise the Java platform, as well as Extendable Markup Language technologies can facilitate the interchange of data and the development of next generation data warehousing and business intelligence applications. While Java technology has been used extensively for client side access and to presentation layer challenges, it is rapidly emerging as a significant tool for developing scaleable server side programs. The Java2 Platform, Enterprise Edition (J2EE) provides the object, transaction, and security support for building such systems.Metadata IssuesOne of the key issues that business intelligence developers must solve is that of incompatible metadata formats. Metadata can be defined as information about data or simply "data about data." In practice, metadata is what most tools, databases, applications, and other information processes use to define, relate, and manipulate data objects within their own environments. It defines the structure and meaning of data objects managed by an application so that the application knows how to process requests or jobs involving those data objects. Developers can use this schema to create views for users. Also, users can browse the schema to better understand the structure and function of the database tables before launching a query.To address the metadata issue, a group of companies have joined to develop the Java Metadata Interface (JMI) API. The JMI API permits the access and manipulation of metadata in Java with standard metadata services. JMI is based on the Meta Object Facility (MOF)specification from the Object Management Group (OMG). The MOF provides a model and a set of interfaces for the creation, storage, access, Metamodel and metadata interchange is done via XML and uses the XML Metadata Interchange (XMI) specification, also from the OMG. JMI leverages Java technology to create an end-to-end data warehousing and business intelligence solutions framework.Enterprise JavaBeansA key tool provided by J2EE is Enterprise JavaBeans (EJB), an architecture for the development of component-based distributed business applications. Applications written using the EJB architecture are scalable, transactional, secure, and multi-user aware. These applications may be written once and then deployed on any server platform that supports J2EE. The EJB architecture makes it easy for developers to write components, since they do not need to understand or deal with complex, system-level details such as thread management, resource pooling, and transaction and security management. This allows for role-based development where component assemblers, platform providers and application assemblers can focus on their area of responsibility further simplifying application development.Data Storage & AccessData stored in existing applications can be accessed with specialized connectors. Integration and interoperability of these data sources is further enabled by the metadata repository that contains metamodels of the data contained in the sources, which then can be accessed and interchanged uniformly via the JMI API. These metamodels capture the essential structure and semantics of business components, allowing them to be accessed and queried via the JMI API or to be interchanged via XML. Through all of these processes, the J2EE infrastructure ensures the security and integrity of the data through transaction management and propagation and the underlying security architecture.To consolidate historical information for analysis of sales and marketing trends, a data warehouse is often the best solution. In this example, data can be extracted from the operational systems with a variety of Extract, Transform and Load tools (ETL). The metamodels allow EJBs designed for filtering, transformation, and consolidation of data to operate uniformly on data from diverse data sources as the bean is able to query the metamodel to identify and extract the pertinent fields. Queries and reports can be run against the data warehouse that containsinformation from numerous sources in a consistent, enterprise-wide fashion through the use of the JMI API.Java in Industrial SettingsMany people know Java only as a tool on the World Wide Web that enables sites to perform some of their fancier functions such as interactivity and animation. However, the actual uses for Java are much more widespread. Since Java is an object-oriented language, the time needed for application development is minimal.In addition, Java's automatic memory management and lack of pointers remove some leading causes of programming errors. Most importantly, application developers do not need to create different versions of the software for different platforms. The advantages available through Java have even found their way into hardware. The emerging new Java devices are streamlined systems that exploit network servers for much of their processing power, storage, content, and administration.Benefits of JavaThe benefits of Java translate across many industries, and some are specific to the control and automation environment. Java's ability to run on any platform enables the organization to make use of the existing equipment while enhancing the application.IntegrationWith few exceptions, applications running on the factory floor were never intended to exchange information with systems in the executive office, but managers have recently discovered the need for that type of information. Before Java, that often meant bringing together data from systems written on different platforms in different languages at different times. Integration was usually done on a piecemeal basis, once it worked, was unique to the two applications it was tying together. Additional integration required developing a brand new system from scratch, raising the cost of integration.ScalabilityAnother benefit of Java in the industrial environment is its scalability. Even when internal compatibility is not an issue, companies often face difficulties when suppliers with whom they share information have incompatible systems. This becomes more of a problem as supply-chain management takes on a more critical role which requires manufacturers to interact more withoffshore suppliers and clients. The greatest efficiency comes when all systems can communicate with each other and share information seamlessly. Since Java is so ubiquitous, it often solves these problems.Dynamic Web Page DevelopmentJava has been used by both large and small organizations for a wide variety of applications beyond consumer oriented websites. Sandia, a multiprogram laboratory of the U.S. Department of Energy's National Nuclear Security Administration, has developed a unique Java application. The lab was tasked with developing an enterprise-wide inventory tracking and equipment maintenance system that provides dynamic Web pages.ConclusionOpen standards have driven the e-business revolution. As e-business continues to develop, various computing technologies help to drive its evolution. The Java programming language and platform have emerged as major technologies for performing e-business functions. the time needed for application development is minimal. Java also encourages good software engineering practices with clear separation of interfaces and implementations as well as easy exception handling. Java's automatic memory management and lack of pointers remove some leading causes of programming errors. The advantages available through Java have also found their way into hardware. The emerging new Java devices are streamlined systems that exploit network servers for much of their processing power, storage, content, and administration.中文翻译:Java编程语言和Java平台，已成为主要的实现电子商务功能的技术。
Java技术介绍-毕业论文外文翻译
Java Technical DescriptionJava as a Programming Platform.Java is certainly a good programming language. There is no doubt that it is one of the better languages available to serious programmers. We think it could potentially have been a great programming language, but it is probably too late for that. Once a language is out in the field, the ugly reality of compatibility with existing code sets in."Java was never just a language. There are lots of programming languages out there, and few of them make much of a splash. Java is a whole platform, with a huge library, containing lots of reusable code, and an execution environment that provides services such as security, portability across operating systems, and automatic garbage collection.As a programmer, you will want a language with a pleasant syntax and comprehensible semantics (i.e., not C++). Java fits the bill, as do dozens of other fine languages. Some languages give you portability, garbage collection, and the like, but they don't have much of a library, forcing you to roll your own if you want fancy graphics or networking or database access. Well, Java has everything—a good language, a high-quality execution environment, and a vast library. That combination is what makes Java an irresistible proposition to so many programmers.Features of Java.1.SimpleWe wanted to build a system that could be programmed easily without a lot of esoteric training and which leveraged today's standard practice. So even though we found that C++ was unsuitable, we designed Java as closely to C++ as possible in order to make the system more comprehensible. Java omits many rarely used, poorly understood, confusing features of C++ that, in our experience, bring more grief than benefit.The syntax for Java is, indeed, a cleaned-up version of the syntax for C++. There is no need for header files, pointer arithmetic (or even a pointer syntax), structures, unions, operator overloading, virtual base classes, and so on. (See the C++ notes interspersed throughout the text for more on the differences between Java and C++.) The designers did not, however, attempt to fix all of the clumsy features of C++. For example, the syntax of the switch statement is unchanged in Java. If you know C++, you will find the transition to the Java syntax easy.If you are used to a visual programming environment (such as Visual Basic), you will not find Java simple. There is much strange syntax (though it does not take long to get the hang of it). More important, you must do a lot more programming in Java. The beauty of Visual Basic is that its visual design environment almost automatically provides a lot of the infrastructure for an application. The equivalent functionality must be programmed manually, usually with a fair bit of code, in Java. There are, however, third-party development environments that provide "drag-and-drop"-style program development.Another aspect of being simple is being small. One of the goals of Java is to enable the construction of software that can run stand-alone in small machines. The size of the basic interpreter and class support is about 40K bytes; adding the basic standard libraries and thread support (essentially a self-contained microkernel) adds an additional 175K.2. Object OrientedSimply stated, object-oriented design is a technique for programming that focuses on the data (= objects) and on the interfaces to that object. To make an analogy with carpentry, an "object-oriented" carpenter would be mostly concerned with the chair he was building, and secondarily with the tools used to make it; a "non-object-oriented" carpenter would think primarily of his tools. The object-oriented facilities of Java are essentially those of C++.Object orientation has proven its worth in the last 30 years, and it is inconceivable that a modern programming language would not use it. Indeed, the object-oriented features of Java are comparable to those of C++. The major differencebetween Java and C++ lies in multiple inheritance, which Java has replaced with the simpler concept of interfaces, and in the Java metaclass model. The reflection mechanism and object serialization feature make it much easier to implement persistent objects and GUI builders that can integrate off-the-shelf components.3. DistributedJava has an extensive library of routines for coping with TCP/IP protocols like HTTP and FTP. Java applications can open and access objects across the Net via URLs with the same ease as when accessing a local file system. We have found the networking capabilities of Java to be both strong and easy to use. Anyone who has tried to do Internet programming using another language will revel in how simple Java makes onerous tasks like opening a socket connection. (We cover networking in Volume 2 of this book.) The remote method invocation mechanism enables communication between distributedobjects (also covered in Volume 2).There is now a separate architecture, the Java 2 Enterprise Edition (J2EE), that supports very large scale distributed applications.4. RobustJava is intended for writing programs that must be reliable in a variety of ways. Java puts a lot of emphasis on early checking for possible problems, later dynamic (run-time) checking, and eliminating situations that are error-prone.… The single biggest difference between Java and C/C++ is that Java has a pointer model that eliminates the possibility of overwriting memory and corrupting data.This feature is also very useful. The Java compiler detects many problems that, in other languages, would show up only at run time. As for the second point, anyone who has spent hours chasing memory corruption caused by a pointer bug will be very happy with this feature of Java.If you are coming from a language like Visual Basic that doesn't explicitly use pointers, you are probably wondering why this is so important. C programmers are not so lucky. They need pointers to access strings, arrays, objects, and even files. In Visual Basic, you do not use pointers for any of these entities, nor do you need to worry about memory allocation for them. On the other hand, many data structures aredifficult to implement in a pointerless language. Java gives you the best of both worlds. You do not need pointers for everyday constructs like strings and arrays. You have the power of pointers if you need it, for example, for linked lists. And you always have complete safety, because you can never access a bad pointer, make memory allocation errors, or have to protect against memory leaking away.5. SecureJava is intended to be used in networked/distributed environments. Toward that end, a lot of emphasis has been placed on security. Java enables the construction of virus-free, tamper-free systems.In the first edition of Core Java we said: "Well, one should 'never say never again,'" and we turned out to be right. Not long after the first version of the Java Development Kit was shipped, a group of security experts at Princeton University found subtle bugs in the security features of Java 1.0. Sun Microsystems has encouraged research into Java security, making publicly available the specification and implementation of the virtual machine and the security libraries. They have fixed all known security bugs quickly. In any case, Java makes it extremely difficult to outwit its security mechanisms. The bugs found so far have been very technical and few in number. From the beginning, Java was designed to make certain kinds of attacks impossible, among them:∙Overrunning the runtime stack—a common attack of worms and viruses Corrupting memory outside its own process space Reading or writing files without permission.∙A number of security features have been added to Java over time. Since version1.1, Java has the notion of digitally signed classesWith a signed class, you can be sure who wrote it. Any time you trust the author of the class, the class can be allowed more privileges on your machine.6. Architecture NeutralThe compiler generates an architecture-neutral object file format—the compiled code is executable on many processors, given the presence of the Java runtime system.The Java compiler does this by generating bytecode instructions which have nothing to do with a particular computerarchitecture. Rather, they are designed to be both easy to interpret on any machine and easily translated into native machine code on the fly.This is not a new idea. More than 20 years ago, both Niklaus Wirth's original implementation of Pascal and the UCSD Pascal system used the same technique. Of course, interpreting bytecodes is necessarily slower than running machine instructions at full speed, so it isn't clear that this is even a good idea. However, virtual machines have the option of translating the most frequently executed bytecode sequences into machine code, a process called just-in-time compilation. This strategy has proven so effective that even Microsoft's .NET platform relies on a virtual machine.The virtual machine has other advantages. It increases security because the virtual machine can check the behavior of instruction sequences. Some programs even produce bytecodes on the fly, dynamically enhancing the capabilities of a running program.7. PortableUnlike C and C++, there are no "implementation-dependent" aspects of the specification. The sizes of the primitive data types are specified, as is the behavior of arithmetic on them.For example, an int in Java is always a 32-bit integer. In C/C++, int can mean a 16-bit integer, a 32-bit integer, or any other size that the compiler vendor likes. The only restriction is that the int type must have at least as many bytes as a short int and cannot have more bytes than a long int. Having a fixed size for number types eliminates a major porting headache. Binary data is stored and transmitted in a fixed format, eliminating confusion about byte ordering. Strings are saved in a standard Unicode format.The libraries that are a part of the system define portable interfaces. For example, there is an abstract Window class and implementations of it for UNIX, Windows, and the Macintosh.As anyone who has ever tried knows, it is an effort of heroic proportions to write a program that looks good on Windows, the Macintosh, and 10 flavors of UNIX. Java1.0 made the heroic effort, delivering a simple toolkit that mapped common user interface elements to a number of platforms.Unfortunately, the result was a library that, with a lot of work, could give barely acceptable results on different systems. (And there were often different bugs on the different platform graphics implementations.) But it was a start. There are many applications in which portability is more important than user interface slickness, and these applications did benefit from early versions of Java. By now, the user interface toolkit has been completely rewritten so that it no longer relies on the host user interface. The result is far more consistent and, we think, more attractive than in earlier versions of Java.8. InterpretedThe Java interpreter can execute Java bytecodes directly on any machine to which the interpreter has been ported. Since linking is a more incremental and lightweight process, the development process can be much more rapid and exploratory.Incremental linking has advantages, but its benefit for the development process is clearly overstated. In any case, we have found Java development tools to be quite slow. If you are used to the speed of the classic Microsoft Visual C++ environment, you will likely be disappointed with the performance of Java development environments. (The current version of Visual Studio isn't as zippy as the classic environments, however. No matter what languageyou program in, you should definitely ask your boss for a faster computer to run the latest development environments. )9. High PerformanceWhile the performance of interpreted bytecodes is usually more than adequate, there are situations where higher performance is required. The bytecodes can be translated on the fly (at run time) into machine code for the particular CPU the application is running on.If you use an interpreter to execute the bytecodes, "high performance" is not the term that we would use. However, on many platforms, there is also another form ofcompilation, the just-in-time (JIT) compilers. These work by compiling the bytecodes into native code once, caching the results, and then calling them again if needed. This approach speeds up commonly used code tremendously because one has to do the interpretation only once. Although still slightly slower than a true native code compiler, a just-in-time compiler can give you a 10- or even 20-fold speedup for some programs and will almost always be significantly faster than an interpreter. This technology is being improved continuously and may eventually yield results that cannot be matched by traditional compilation systems. For example, a just-in-time compiler can monitor which code is executed frequently and optimize just that code for speed.10. MultithreadedThe enefits of multithreading are better interactive responsiveness and real-time behavior.if you have ever tried to do multithreading in another language, you will be pleasantly surprised at how easy it is in Java. Threads in Java also can take advantage of multiprocessor systems if the base operating system does so. On the downside, thread implementations on the major platforms differ widely, and Java makes no effort to be platform independent in this regard. Only the code for calling multithreading remains the same across machines; Java offloads the implementation of multithreading to the underlying operating system or a thread library. Nonetheless, the ease of multithreading is one of the main reasons why Java is such an appealing language for server-side development.11. DynamicIn a number of ways, Java is a more dynamic language than C or C++. It was designed to adapt to an evolving environment. Libraries can freely add new methods and instance variables without any effect on their clients. In Java, finding out run time type information is straightforward.This is an important feature in those situations in which code needs to be added to a running program. A prime example is code that is downloaded from the Internet to run in a browser. In Java 1.0, finding out runtime type information was anything but straightforward, but current versions of Java give the programmer full insight intoboth the structure and behavior of its objects. This is extremely useful for systems that need to analyze objects at run time, such as Java GUI builders, smart debuggers, pluggable components, and object databases.Java技术介绍Java是一种程序设计平台Java是一种优秀的程序设计语言。
java中常用英文简写全拼与中文意思
API (Application Programming Interface) 应用编程接口JRE (Java Runtime Enviroment) Java 运行时环境JDK (Java Development Kit) Java开发工具包SDK（Software Development Kit, 即软件开发工具包）JVM (Java Virtual Machine) Java虚拟机JNI (Java Native Interface) Java本地接口AWT (Abstract Windows Toolekit) 抽象窗口工具箱JNDI (Java Naming & Directory Interface) JAVA命名目录服务.主要提供的功能是：提供一个目录系统，让其它各地的应用程序在其上面留下自己的索引，从而满足快速查找和定位分布式应用程序的功能。
JMS (Java Message Service)JAVA消息服务.主要实现各个应用程序之间的通讯.包括点对点和广播.JTA (Java Transcation API) JAVA事务服务.提供各种分布式事务服务.应用程序只需调用其提供的接口即可.JAF (Java Action FrameWork) JAVA安全认证框架.提供一些安全控制方面的框架.让开发者通过各种部署和自定义实现自己的个性安全控制策略.RMI (Remote Method Interface) 远程方法调用CVS (Concurrent Versions System) 版本控制器SVN (Subversion) 版本控制器TC (Test Case) 测试用例，是为某个特殊目标而编制的一组测试输入、执行条件以及预期结果，以便测试某个程序路径或核实是否满足某个特定需求。
指对一项特定的软件产品进行测试任务的描述，体现测试方案、方法、技术和策略。
内容包括测试目标、测试环境、输入数据、测试步骤、预期结果、测试脚本等，并形成文档。
Java外文翻译
附件1：外文资料翻译译文图形用户接口一个基本的设计方针是“简单的事情变得容易，困难的事情成为可能。
”劳在Java的图形用户界面（GUI）库原设计目标是允许程序员建立一个GUI ，在所有平台上看起来好。
这一目标没有实现。
相反，Java的罗湖抽象窗口工具包（AWT ）产生一个GUI，看着所有系统上同样表现平平。
此外，它是限制性的，你可以用四种字体，你不能访问任何更复杂的GUI 元素，在你的操作系统存在。
也尴尬和非面向对象的Java 1.0 AWT编程模型。
一个学生在我的一个研讨会（曾在Sun公司一直在创造Java的）解释原因：原来的AWT已经构思，设计，并在一个月内实施。
一定的生产力的奇迹，也是为什么设计对象的教训是非常重要的。
Java 1.1 AWT的事件模型，这需要一个更清晰的，面向对象的方法的JavaBeans组件的编程模型是面向可视化编程环境容易创造此外，情况有所好转。
的Java 2（JDK 1.2 ），基本上取代Java基础类（JFC），被称为GUI部分的所有“摇摆完成了转型。
”从旧的Java 1.0 AWT的这是一个易于使用的一整套丰富，易于理解的JavaBeans ，可以拖动和下降（以及手工编程），以建立一个合理的GUI 。
“第三次修订版”的软件产业规则（一个产品是不是良好，直到第三次修订版），似乎与编程语言也是如此。
本章介绍了现代的Java Swing库，使得Swing是Sun公司的最终目的地的GUI库，为Java.2合理的假设，如果你有一些原因，因为你支持旧的代码，你需要使用原有的“老”的AWT （或浏览器的限制），你可以找到介绍，在这本书的第一版在下载。
请注意，一些AWT 组件保持在Java中，并在某些情况下，你必须使用他们。
请注意，这是不是所有的Swing组件或描述类的所有方法的综合词汇。
你在这里看到的是一个简单的介绍。
Swing库是巨大的，本章的目的是只让你的要领和舒适的概念开始。
(完整word版)JAVA外文文献+翻译
燕山大学本科生毕业设计（翻译）1 Java and the InternetIf Java is, in fact, yet another computer programming language, you may question why it is so important and why it is being promoted as a revolutionarystep in computer programming. The answer isn ’t immediately obvious if you coming from a traditional programming perspective. Although Java is very useful for solving traditional stand-alone programming problems, it is also important because it will solve programming problems on the World Wide Web.1.Client-side programmingThe Web ’s in itial server-browser design provided for interactive content, but the interactivity was completely provided by the server. The server produced static pages for the client browser, which would simply interpret and display them. Basic HTML contains simple mechanisms f or data gathering: text-entry boxes, check boxes, radio boxes, lists and drop-down lists, as well as a button that can only be programmed to reset the data on the form or“submit ”on the form back to the server. This submission passes t hrough the Common Gateway Interface (CGI) provided on all Web servers. The text within the submission tells CGI what to do with it. The most common action is to run a program located on the server in a directory that ’s typically called “-bin.” (If you watch the address w indow at the top of your browser when you push a button on a Web page, you can sometimes see “cgi -bin ” within all the gobbledygook there.) These programs can be written in most languages. Perl is a common choice because it is designed for text manipulation and is interpreted, so it can be installed on any server regardless of processor or operating system. Many powerful Web sites today are built strictly on CGI, and you can in fact do nearly anything with it. However, Web sites built on CGI programs can rapidly become overly complicated to maintain, and there is also the problem of response time. The response of a CGI program depends on how much data must。
外文翻译java
外文资料译文及原文JavaJava I/O 系统对编程语言的设计者来说，创建一套好的输入输出（I/O）系统，是一项难度极高的任务。
这一点可以从解决方案的数量之多上看出端倪。
这个问题难就难在它要面对的可能性太多了。
不仅是因为有那么多 I/O 的源和目地（文件，控制台，网络连接等等）,而且还有很多方法（顺序的『sequential』,随机的『random-access』, 缓存的『 buffered 』，二进制的『 binary 』，字符方式的『 character 』，行的『by lines 』，字的『 by words 』，等等）。
Java类库的设计者们用"创建很多类"的办法来解决这个问题。
坦率地说Java I/O 系统的类实在是太多了，以至于初看起来会把人吓着（但是，具有讽刺意味的是，这种设计实际上是限制了类的爆炸性增长）。
此外，Java在1.0版之后又对其 I/O 类库作了重大的修改，原先是面向 byte 的，现在又补充了面向Unicode字符的类库。
为了提高性能，完善功能，JDK1.4又加了一个nio（意思是"new I/O"。
这个名字会用上很多年）。
这么以来，如果你想对Java的I/O 类库有个全面了解，并且做到运用自如，你就得先学习大量的类。
此外，了解 I/O 类库的演化的历史也是相当重要的。
可能你的第一反应是 "别拿什么历史来烦我了，告诉我怎么用就可以了！ "但问题是，如果你对这段历史一无所知，很快就会被一些有用或是没用的类给搞糊涂了。
本章会介绍 Java 标准类库中的各种 I/O 类，及其使用方法。
File 类在介绍直接从流里读写数据的类之前，我们先介绍一下处理文件和目录的类。
File 类有一个极具欺骗性的名字；或许你会认为这是一个关于文件的类，但它不是。
你可以用它来表示某个文件的名字，也可以用它来表示目录里一组文件的名字。
java中英文对照
1 . Introduction To Objects1.1The progress of abstractionAll programming languages provide abstractions. It can be argued that the complexity of the problems you’re able to solve is directly related to the kind and quality of abstraction. By “kind” I mean, “What is it that you are abstracting?” Assembly language is a small abstraction of the underlying machine. Many so-called “imperative” languages that followed (such as FORTRAN, BASIC, and C) were abstractions of assembly language. These languages are big improvements over assembly language, but their primary abstraction still requires you to think in terms of the structure of the computer rather than the structure of the problem you are trying to solve. The programmer must establish the association between the machine model (in the “solution space,” which is the place where you’re modeling that problem, such as a computer) and the model of the problem that is actually being solved (in the “problem space,” which is the place where the problem exists). The effort required to perform this mapping, and the fact that it is extrinsic to the programming language, produces programs that are difficult to write and expensive to maintain, and as a side effect created the entire “programming methods” industry.The alter native to modeling the machine is to model the problem you’re trying to solve. Early languages such as LISP and APL chose particular views of the world (“All problems are ultimately lists” or “All problems are algorithmic,” respectively). PROLOG casts all problems into chains of decisions. Languages have been created for constraint-based programming and for programming exclusively by manipulating graphical symbols. (The latter proved to be too restrictive.) Each of these approaches is a good solution to the particular class of problem they’re designed to solve, but when you step outside of that domain they become awkward.The object-oriented approach goes a step further by providing tools for the programmer to represent elements in the problem space. This representation is general enough that the programmer is not constrained to any particular type of problem. We refer to the elements in the problem space and their representations in the solution space as “objects.” (You will also need other objects that don’t have problem-space analogs.) The idea is that the program is allowed to adapt itself to the lingo of the problem by adding new types of objects, sowhen you read the code describing the solution, you’re reading words that also express the problem. This is a more flexible and powerful language abstraction than what we’ve had before. Thus, OOP allows you to describe the problem in terms of the problem, rather than in terms of the computer where the solution will run. There’s still a connection back to the computer: each object looks quite a bit like a little computer—it has a state, and it has operations that you can ask it to perform. However, this doesn’t seem like such a bad analogy to objects in the real world—they all have characteristics and behaviors.Alan Kay summarized five basic characteristics of Smalltalk, the first successful object-oriented language and one of the languages upon which Java is based. These characteristics represent a pure approach to object-oriented programming:1.Everything is an object.Think of an object as a fancy variable; it stores data, but you can “makerequests” to that object, asking it to perform operations on itself. In theory, you can take any conceptual component in the problem you’re trying to solve (dogs, building s, services, etc.) and represent it as an object in your program.2. A program is a bunch of objects telling each other what to do by sending messages. To make arequest of an object, you “send a message” to that object. More concretely, you can think of a m essage as a request to call a method that belongs to a particular object.3.Each object has its own memory made up of other objects. Put another way, you create a new kindof object by making a package containing existing objects. Thus, you can build complexity into a program while hiding it behind the simplicity of objects.4.Every object has a type. Using the parlance, each object is an instance of a class, in which “class” issynonymous with “type.” The most important distinguishing characteristic of a class is “What messages can you send to it?”5.All objects of a particular type can receive the same messages. This is actually a loaded statement,as you will see later. Because an object of type “circle” is also an object of type “shape,” a circle is guaranteed to accept shape messages. This means you can write code that talks to shapes and automatically handle anything that fits the description of a shape. This substitutability is one of the powerful concepts in OOP.Booch offers an even more succinct description of an object:An object has state, behavior and identity.This means that an object can have internal data (which gives it state), methods (to produce behavior), and each object can be uniquely distinguished from every other object—to put this in a concrete sense, each object has a unique address in memory.1.2 An object has an interfaceAristotle was probably the first to begin a careful study of the concept of type;he spoke of “the class of fishes and the class of birds.” The idea that all objects, while being unique, are also part of a class of objects that have characteristics and behaviors in common was used directly in the first object-oriented language, Simula-67, with its fundamental keyword class that introduces a new type into a program.S imula, as its name implies, was created for developing simulations such as the classic “bank teller problem.” In this, you have a bunch of tellers, customers, accounts, transactions, and units of money—a lot of “objects.” Objects that are identical except for their state during a program’s execution are grouped together into “classes of objects” and that’s where the keyword class came from. Creating abstract data types (classes) is a fundamental concept in object-oriented programming. Abstract data types work almost exactly like built-in types: You can create variables of a type (called objects or instances in object-oriented parlance) and manipulate those variables (called sending messages or requests; you send a message and the object figures out what to do with it). The members (elements) of each class share some commonality: every account has a balance, every teller can accept a deposit, etc. At the same time, each member has its own state: each account has a different balance, each teller has a name. Thus, the tellers, customers, accounts, transactions, etc., can each be represented with a unique entity in the computer program. This entity is the object, and each object belongs to a particular class that defines its characteristics and behaviors.So, although what we really do in object-oriented programming is create new data types, virtually all object-oriented programming languages use the “class” keyword. When you see the word “type” think “class” and vice versa.Since a class describes a set of objects that have identical characteristics (data elements) and behaviors (functionality), a class is really a data type because a floating point number, for example, also has a set ofcharacteristics and behaviors. The difference is that a programmer defines a class to fit a problem rather than being forced to use an existing data type that was designed to represent a unit of storage in a machine. You extend the programming language by adding new data types specific to your needs. The programming system welcomes the new classes and gives them all the care and type-checking that it gives to built-in types.The object-oriented approach is not limited to building simulations. Whether or not you agree that any program is a simulation of the system you’re designing, the use of OOP techniques can easily reduce a large set of problems to a simple solution.Once a class is established, you can make as many objects of that class as you like, and then manipulate those objects as if they are the elements that exist in the problem you are trying to solve. Indeed, one of the challenges of object-oriented programming is to create a one-to-one mapping between the elements in the problem space and objects in the solution space.But how do you get an object to do useful work for you? There must be a way to make a request of the object so that it will do something, such as complete a transaction, draw something on the screen, or turn on a switch. And each object can satisfy only certain requests. The requests you can make of an object are defined by its interface, and the type is what determines the interface. A simple example might be a representation of a light bulb:Light lt = new Light();lt.on();The interface establishes what requests you can make for a particular object. However, there must be code somewhere to satisfy that request. This, along with the hidden data, comprises the implementation. From a procedural programming standpoint, it’s not that complicated. A type has a method associated with each possible request, and when you make a particular request to an object, that method is called. This process isusually summarized by saying that you “send a message” (make a request) to an object, and the object figures out what to do with that message (it executes code).Here, the name of the type/class is Light, the name of this particular Light object is lt,and the requests that you can make of a Light object are to turn it on, turn it off, make it brighter, or make it dimmer. You create a Light object by defining a “reference” (lt) for that object and calling new to request a new object of that type. To send a message to the object, you state the name of the object and connect it to the message request with a period (dot). From the standpoint of the user of a predefined class, that’s pretty much all there is to programming with objects.The preceding diagram follows the format of the Unified Modeling Language(UML). Each class is represented by a box, with the type name in the top portion of the box, any data members that you care to describe in the middle portion of the box, and the methods(the functions that belong to this object, which receive any messages you send to that object) in the bottom portion of the box. Often, only the name of the class and the public methods are shown in UML design diagrams, so the middle portion is not shown. If you’re interested only in the class name, then the bottom portion doesn’t need to be shown, either1.3 An object provides services.While you’re trying to develop or understand a program design, one of the best ways to think about objects is as “service providers.” Your program itself will provide services to the user, and it will accomplish this by using the services offered by other objects. Your goal is to produce (or even better, locate in existing code libraries) a set of objects that provide the ideal services to solve your problem.A way to start doing this is to ask “if I could magically pull them out of a hat, what objects would solve my problem right away?” For example, suppose you are creating a bookkeeping program. You might imagine some objects that contain pre-defined bookkeeping input screens, another set of objects that perform bookkeeping calculations, and an object that handles printing of checks and invoices on all different kinds of printers. Maybe some of these objects alread y exist, and for the ones that don’t, what would they look like? What services would those objects provide, and what objects would they need to fulfill their obligations? If you keep doing this, you will eventually reach a point where you can say either “t hat object seems simpleenough to sit down and write” or “I’m sure that object must exist already.” This is a reasonable way to decompose a problem into a set of objects.Thinking of an object as a service provider has an additional benefit: it helps to improve the cohesiveness of the object. High cohesion is a fundamental quality of software design: It means that the various aspects of a software component (such as an object, although this could also apply to a method or a library of objects) “fit togethe r” well. One problem people have when designing objects is cramming too much functionality into one object. For example, in your check printing module, you may decide you need an object that knows all about formatting and printing. You’ll probably discover that this is too much for one object, and that what you need is three or more objects. One object might be a catalog of all the possible check layouts, which can be queried for information about how to print a check. One object or set of objects could be a generic printing interface that knows all about different kinds of printers (but nothing about bookkeeping—this one is a candidate for buying rather than writing yourself). And a third object could use the services of the other two to accomplish the task. Thus, each object has a cohesive set of services it offers. In a good object-oriented design, each object does one thing well, but doesn’t try to do too much. As seen here, this not only allows the discovery of objects that might be purchased (the printer interface object), but it also produces the possibility of an object that might be reused somewhere else (the catalog of check layouts).Treating objects as service providers is a great simplifying tool, and it’s very useful not only during the design process, but also when someone else is trying to understand your code or reuse an object—if they can see the value of the object based on what service it provides, it makes it much easier to fit it into the design.1. 对象入门1.1 抽象的进步所有编程语言的最终目的都是提供一种“抽象”方法。
java介绍外文翻译
外文原文Introduction to Javaautor：Martin Ngobye.source：Computing Static Slice for Java ProgramsJava is designed to meet the challenges of application development in the context of heterogeneous, network-wide distributed environments. Paramount among these challenges is secure delivery of applications that consume the minimum of system resources, can run on any hardware and software platform, and can be extended dynamically.Java originated as part of a research project to develop advanced software for a wide variety of network devices and embedded systems. The goal was to develop a small, reliable, portable, distributed, real-time operating platform. When the project started, C++ was the language of choice. But over time the difficulties encountered with C++ grew to the point where the problems could best be addressed by creating an entirely new language platform. Design and architecture decisions drew from a variety of languages such as Eiffel, SmallTalk, Objective C, and Cedar/Mesa. The result is a language platform that has proven ideal for developing secure, distributed, network based end-user applications in environments ranging from network-embedded devices to the World-Wide Web and the desktop.The design requirements of Java are driven by the nature of the computing environments in which software must be deployed.The massive growth of the Internet and the World-Wide Web leads us to a completely new way of looking at development and distribution of software. To live in the world of electronic commerce and distribution, Java must enable the development of secure, high performance, and highly robust applications on multiple platforms in heterogeneous, distributed networks.Operating on multiple platforms in heterogeneous networks invalidates the traditional schemes of binary distribution, release, upgrade, patch, and so on. To survive in this jungle, Java must be architecture neutral, portable, and dynamically adaptable.The Java system that emerged to meet these needs is simple, so it can be easily programmed by most developers; familiar, so that current developers can easily learn Java; object oriented, to take advantage of modern software development methodologies and to fit into distributed client-server applications; multithreaded, for high performance in applications that need to perform multiple concurrent activities, such as multimedia; and interpreted, for maximum portability and dynamic capabilities.Together, the above requirements comprise quite a collection of buzzwords, so let’s examine some of them and their respective benefits before going on.What’s completely new is the manner in which Java and its run-time system have combinedthem to produce a flexible and powerful programming system..Developing your applications using Java results in software that is portable across multiple machine architectures, operating systems, and graphical user interfaces, secure, and high performance, With Java, your job as a software developer is much easier—you focus your full attention on the end goal of shipping innovative products on time, based on the solid foundation of Java. The better way to develop software is here, now, brought to you by the Java language platform.Very dynamic languages like Lisp, TCL, and SmallTalk are often used for prototyping. One of the reasons for their success at this is that they are very robust—you don’t have to worry about freeing or corrupting memory.Similarly, programmers can be relatively fearless about dealing with memory when programming in Java, The garbage collection sy stem makes the programmer’s job vastly easier; with the burden of memory management taken off the programmer’s shoulders, storage allocation errors go away. Another reason commonly given that languages like Lisp, TCL, and SmallTalk are good for prototyping is that they don’t require you to pin down decisions early on—these languages are semantically rich.Java has exactly the opposite property: it forces you to make explicit choices. Along with these choices come a lot of assistance—you can write method invocations and, if you get something wrong, you get told about it at compile time. You don’t have to worry about method invocation error.The Java beginner must grasp 30 basic conceptsBasic concept1.In OOP the only relations is what the object’s interface, such as the computer seller he leaves alone internal structure of electrical source, but he is only concerned about that whether the power will be supplied to you, also so long as know can or not but is not how and why.All procedures are make up of certain attribute and the behavior object, the different object visit invokes through the function invocation, between the object all intercommunion are invoke through the method invocation, By object data encapsulation, enhances reuse rate very much..2.In OOP the most important thought is class, the class is the template ,is a blueprint, construct an object from a class, namely construct an instance of the class.3. Encapsulation: is that combines the data and the behavior in a package) and hides the data the realization process to the object user, in an object data is called its instance field.4.Through expands a class to obtain a new class is called inheritance, but all classes are constructed by the object super root class of expansion, super root class of as follows can make the introduction.5.Object 3 principal characteristicsBehavior--- explained this object can make what.Tate--- when the object exerts the method object reflection.Dentity--- and other similar behavior objects discrimination symbols.Each object has only indentity and among three characteristics they affect mutually.6. Relations among classes:Use-a:Dependent relationHas-a:Polymerization relationIs-a: inheritor relation -- example:A class has inherited B class, this time A class not only has B class of method, but also has its own method(Individuality exists in general character)7.Structure object use structure:Structure proposing, the structure is one special method, the structure object and to its initialization.Example:A Data class of structure calls DataNew Data () --- structure a new object, also initialize current time.Data happyday=new Data () --- an object evaluates an variable happyday, thus enables this object to be used many times, here be stated the cause variable and the object variable are different.New returns the value is a quotation.Constructor characteristic:The constructor may have 0, one or many parametersThe constructor and the class have the same nameA class may have many constructor. The constructor has not returned valueThe constructor always be together used with the new operator8. Over loading: When many methods have the same name when includes the different parameter, then has the over loading Which method does the compiler have to choose invokes.9.Package : Java allow one or many classes to become together as group, is called package, to organizing duty easily, the standard Java storehouse divides into many packages ng java.Util java, net and so on, the package is layered and all java packages are in java and in a javax package.10. Extendable thought: permit to construct new class on existing classes , when you extend the class which already existed, then you reuse this class of method and the field, at the same time you might add the new method and the field in the new class.11.Expandable class:The expandable class fully manifested is-a to extend the relations The form is:Class (subclass) extends (base class).12. Multi-modality: In java, the object variable is multi-modality But in java does not support multiple extend.13.Dynamic combine: the mechanism of invoking object method mechanism.1) compiler examines object statement type and method name.2) the compiler examines that method invokes parameter type.3) static combine: If the method type is priavte static the final ,compiler can accurately know which method should invoke.4) when the procedure runs and uses dynamic combine to invoke a method, the method edition which then hypothesized machine must invoke x the object actual type which aims at to match.5) dynamic combine: is a very important characteristic, it can cause the procedure to change again may expand but does not need to translate has saved the code.14.Final class:In order to prevent other people derive the new class from yours class, this class is cannot expanded.15.The dynamic invocation spend longer time than the static invocation expenditure.16.Abstract class:Stipulated or many abstract methods class of itself must define is abstract.Example: Public abstract string getDescripition17.In Java each class is be extended by object class.18. equal and toString method in object class .Equal uses in testing an object is whether equal with another object.ToString returns to represent this object the string of character, each class can nearly over loading this method, in order to returns to the current condition the correct expression.(The toString method is a very important method)19.General programming:Any class of type all values all may replace with a object class of variable.20.The array tabulates: The ArrayList dynamic array tabulates, is a class of storehouse, defines in java.In uitl package, but automatic control array size.21.in class and class of object ,getclass method returns to the class type an example, when the procedure start contains can increase in the main method class, hypothesized confidential increase all classes which he needs, each increase class all must increase the class which it needs.22.The class: class might dynamic operate the java code for the compilation the procedure to provide the formidable function reflection, this function was JavaBeans is specially useful, the use reflected Java to be able to support the VB programmer to be familiar with the use the tool.1) when run analysis class ability.2) when run searches observes a class of object.3) realizes the general array operation code.4) provides the method object.But this mechanism mainly aims at the tool but not the application and the procedure.In the reflection mechanism most important part is that permits class that you inspectstructure. With to API includes:Method pointer: Java does not have the method pointer, makes a method address another method, may invoke it in behind, but the interface is the better solution.23. interface: should showing class could do what but not to assign how to do, a class may realize one or many interfaces.24.The interface is not a class, but is to conforms to a interface request class of set of standard.If realizes a interface to need 2 steps:1) the statement class needs to realize assigns the interface.2) provides in the interface all methods definition.Stated a class realizes a interface to need to use the implements key wordsClass actionB implements Comparable its actionb needs to provide the CompareTo method, the interface is not the class, cannot use a new example interface.25.A class only then a super class, but a class can realize many interfaces. In a Java important interface: Cloneable26.The interface and call-back :to programs a commonly used pattern is call-back,in the pattern, you may refer when this class of pattern settled specific time occurs returns to adjusts on the object the method.Example:ActionListener interface monitor.Similar API includes:27.Object clone:The clone method is a object protection method, this meant your code cannot simple invoke it.28.Inner class an inner class definition is the definition in another class.The reason is:1) an inner class object can visit founds its object realization, including private data.2) about other classes in the same package in that, inner class can be hided.3) the anonymous inner class may the very convenient definition accent.In 4) uses the category to be possible the extremely convenient compilation event driver.29.Agent class (proxy):1) appointing all codes that interfaces request2) all methods (toString equals) that object class define30.Data type:Java is kind of emphasizing type language, each variable all must be declared its types at first, in java altogether has 8 basic types . four kinds are the long, two kinds are the float, one is the char, being used in the Unicode code char, Boolean.1. java is simpleJava and C + + are very similar, but much simpler. All the high-level programminglanguage features, is not absolutely necessary have been deleted. For example, Java does not overload operator, the title of the document, pre-processing, computing pointer, the structure of the joint, multi-dimensional array, templates and implicit type conversion. If you know a little C, C + + or Pascal, you will soon master Java. Here is a simple procedure JavaHelloWorld: publicclassHelloInternet (publicstaticvoidmain (Stringargv []) (System. out. println ( "HelloIn-ternet!")))2. Java is object-orientedJava is an object-oriented programming language. In addition to the simple types, such as digital and Boolean operators in addition, Java is an object of most. As with any object-oriented languages, Java code also organized by category. Each category provides a definition of the object behavior. Another type of succession can be a kind of behavior. In the category of the root level, often the target category. Java support for the single type of inherited hierarchy. This means that each category can only inherit one other category. Some of the language to allow multiple inheritance, but it may cause confusion and unnecessarily complicated language. For example, imagine that an object would inherit two completely different category. Java also supports the kind of summary of the interface. This allows programmers to define the interface methods, and do not have to rush immediately to determine the methods to achieve. A type of interface can be a number of purposes in order to truly multi-inheritance of a number of advantages. The implementation of an object can be any number of interfaces. IDL interface and Java interface very similar. Very easy to set up IDLJ compiler. In other words, Java can be used to create a CORBA object system distributed object system. In the view of many computer systems use IDL interface and CORBA objects, such compatibility is important.3. Java is a type of staticIn a Java program, it is essential to the definition used by the target (number of characters, such as an array) type. This will help programmers quickly found because the procedure when the compiler can detect the type of error. However, Java System objects are also dynamic types. A requirement for the type of dynamic is often possible, so programmers can write the procedures for different types of objects to do different things.4. Is a Java-based compilerWhen running Java programs, which were first compiled into byte code. Byte code is very similar to the machine instructions, so Java program is very efficient. However, the byte code does not specifically for a particular machine, so no need to recompile Java program can be in many different computer implementation. Java source code files were compiled into a category, whichis equivalent to process byte code performance. In a Java class file, and an example for all of the variables are in the light of, and for the first time in the implementation of the code be resolved. This makes the code more common and more easily subject to revision, but still high.5. Java is architecture neutralJava language is the same for each computer. For example, simple types are the same: 32-bit integer always, always 64-bit long integers. It is strange, such as C and C + + programming language, and so fashionable it is not the case. As a result of these languages so the definition of freedom, each of the compiler and development environment will be different, so that this process nuisance become a transplant. Java programs can easily gain access to transplants, and there is no need to re-compile.6. Java is a soundJava program can not be caused by the collapse of the computer. Java careful testing of the system memory of each visit, make sure it is legitimate and will not cause any problems. However, even if the Java program may also be wrong. If there is some kind of unexpected things, the process will not collapse, and to abandon the exception. Procedures for such an exception would be found to address them. Traditional computer programs can access the full memory. May (unconsciously) to amend any of the value of memory, which will cause problems. Java program can only access memory to allow them access to those parts of the Java program can not modify it does not seek to change the value.7. Java is a compactAs the Java is designed to run on a small computer, as a programming language for the system is relatively small. It effectively in more than 4MB of RAM to run on PC machine. Java translator occupied by only a few hundred KB. This translator for the Java platform independence and portability is reliable. Due to Java is very small, it is a very small computer memory, such as the Java-based PC, as well as television sets, ovens, telephone and home computer, and so on, it is ideal.8. Java is a multi-threadedJava program can run more than one thread. For example, it can be a thread in a time-consuming to complete the calculation, and other users to interact with the threads of dialogue. Therefore, users do not have to stop working, waiting for the Java computing time-consuming process. In the multi-threaded programming environment, it is often difficult because many things may occur at the same time. However, Java provides easy-to-use features simultaneously, so that the programming easier.中文翻译JAVA介绍作者：Martin Ngobye.出处：Computing Static Slice for Java ProgramsJava是被设计用来解决在上下文分布式的异构网络中应用程序开发的问题。
Java技术外文翻译文献
Java技术外文翻译文献(文档含中英文对照即英文原文和中文翻译)外文：Core Java™ Volume II–Advanced Features When Java technology first appeared on the scene, the excitement was not about a well-crafted programming language but about the possibility of safely executing applets that are delivered over the Internet (see V olume I, Chapter 10 for more information about applets). Obviously, delivering executable applets is practical only when the recipients are sure that the code can't wreak havoc on their machines. For this reason, security was and is a major concern of both the designers and the users of Java technology. This means that unlike other languages andsystems, where security was implemented as an afterthought or a reaction to break-ins, security mechanisms are an integral part of Java technology.Three mechanisms help ensure safety:•Language design features (bounds checking on arrays, no unchecked type conversions, no pointer arithmetic, and so on).•An access control mechanism that controls what the code can do (such as file access, network access, and so on).•Code signing, whereby code authors can use standard cryptographic algorithms to authenticate Java code. Then, the users of the code can determine exactly who created the code and whether the code has been altered after it was signed.Below, you'll see the cryptographic algorithms supplied in the java.security package, which allow for code signing and user authentication.As we said earlier, applets were what started the craze over the Java platform. In practice, people discovered that although they could write animated applets like the famous "nervous text" applet, applets could not do a whole lot of useful stuff in the JDK 1.0 security model. For example, because applets under JDK 1.0 were so closely supervised, they couldn't do much good on a corporate intranet, even though relatively little risk attaches to executing an applet from your company's secure intranet. It quickly became clear to Sun that for applets to become truly useful, it was important for users to be able to assign different levels of security, depending on where the applet originated. If an applet comes from a trusted supplier and it has not been tampered with, the user of that applet can then decide whether to give the applet more privileges.To give more trust to an applet, we need to know two things:•Where did the applet come from?•Was the code corrupted in transit?In the past 50 years, mathematicians and computer scientists have developed sophisticated algorithms for ensuring the integrity of data and for electronic signatures. The java.security package contains implementations of many of these algorithms. Fortunately, you don't need to understand the underlying mathematics to use the algorithms in the java.security package. In the next sections, we show you how message digests can detect changes in data files and how digital signatures can prove the identity of the signer.A message digest is a digital fingerprint of a block of data. For example, the so-called SHA1 (secure hash algorithm #1) condenses any data block, no matter how long, into a sequence of 160 bits (20 bytes). As with real fingerprints, one hopes that no two messages have the same SHA1 fingerprint. Of course, that cannot be true—there are only 2160 SHA1 fingerprints, so there must be some messages with the same fingerprint. But 2160is so large that the probability of duplication occurring is negligible. How negligible? According to James Walsh in True Odds: How Risks Affect Your Everyday Life (Merritt Publishing 1996), the chance that you will die from being struck by lightning is about one in 30,000. Now, think of nine other people, for example, your nine least favorite managers or professors. The chance that you and all of them will die from lightning strikes is higher than that of a forged message having the same SHA1 fingerprint as the original. (Of course, more than ten people, none of whom you are likely to know, will die from lightning strikes. However, we are talking about the far slimmer chance that your particular choice of people will be wiped out.)A message digest has two essential properties:•If one bit or several bits of the data are changed, then the message digest also changes.• A forger who is in possession of a given message cannot construct a fake message that has the same message digest as the original.The second property is again a matter of probabilities, of course. Consider the following message by the billionaire father:"Upon my death, my property shall be divided equally among my children; however, my son George shall receive nothing."That message has an SHA1 fingerprint of2D 8B 35 F3 BF 49 CD B1 94 04 E0 66 21 2B 5E 57 70 49 E1 7EThe distrustful father has deposited the message with one attorney and the fingerprint with another. Now, suppose George can bribe the lawyer holding the message. He wants to change the message so that Bill gets nothing. Of course, that changes the fingerprint to a completely different bit pattern:2A 33 0B 4B B3 FE CC 1C 9D 5C 01 A7 09 51 0B 49 AC 8F 98 92Can George find some other wording that matches the fingerprint? If he had been the proud owner of a billion computers from the time the Earth was formed, each computing a million messages a second, he would not yet have found a message he could substitute.A number of algorithms have been designed to compute these message digests. The two best-known are SHA1, the secure hash algorithm developed by the National Institute of Standards and Technology, and MD5, an algorithm invented by Ronald Rivest of MIT. Both algorithms scramble the bits of a message in ingenious ways. For details about these algorithms, see, for example, Cryptography and Network Security, 4th ed., by William Stallings (Prentice Hall 2005). Note that recently, subtle regularities have been discovered in both algorithms. At this point, most cryptographers recommend avoiding MD5 and using SHA1 until a stronger alternative becomes available.The Java programming language implements both SHA1 and MD5. The MessageDigest class is a factory for creating objects that encapsulate the fingerprinting algorithms. It has a static method, called getInstance, that returns an object of a class that extends the MessageDigest class. This means the MessageDigest class serves double duty:•As a factory class•As the superclass for all message digest algorithmsFor example, here is how you obtain an object that can compute SHA fingerprints:MessageDigest alg = MessageDigest.getInstance("SHA-1");(To get an object that can compute MD5, use the string "MD5" as the argument to getInstance.)After you have obtained a MessageDigest object, you feed it all the bytes in the message by repeatedly calling the update method. For example, the following code passes all bytes in a file to the alg object just created to do the fingerprinting：InputStream in = . . .int ch;while ((ch = in.read()) != -1)alg.update((byte) ch);Alternatively, if you have the bytes in an array, you can update the entire array at once:byte[] bytes = . . .;alg.update(bytes);When you are done, call the digest method. This method pads the input—as required by the fingerprinting algorithm—does the computation, and returns the digest as an array of bytes.byte[] hash = alg.digest();The program in Listing 9-15 computes a message digest, using either SHA or MD5. You can load the data to be digested from a file, or you can type a message in the text area.Message SigningIn the last section, you saw how to compute a message digest, a fingerprint for the original message. If the message is altered, then the fingerprint of the altered message will not match the fingerprint of the original. If the message and its fingerprint are delivered separately, then the recipient can check whether the message has been tampered with. However, if both the message and the fingerprint were intercepted, it is an easy matter to modify the message and then recompute the fingerprint. After all, the message digest algorithms are publicly known, and they don't require secret keys. In that case, the recipient of the forged message and the recomputed fingerprint would never know that the message has been altered. Digital signatures solve this problem.To help you understand how digital signatures work, we explain a few concepts from the field called public key cryptography. Public key cryptography is based on the notion of a public key and private key. The idea is that you tell everyone in the world your public key. However, only you hold the private key, and it is important that you safeguard it and don't release it to anyone else. The keys are matched by mathematical relationships, but the exact nature of these relationships is not important for us.The keys are quite long and complex. For example, here is a matching pair of public and private Digital Signature Algorithm (DSA) keys.Public key:Code View:p:fca682ce8e12caba26efccf7110e526db078b05edecbcd1eb4a208f3ae1617ae01f35b91a47e6df 63413c5e12ed0899bcd132acd50d99151bdc43ee737592e17q: 962eddcc369cba8ebb260ee6b6a126d9346e38c5g:678471b27a9cf44ee91a49c5147db1a9aaf244f05a434d6486931d2d14271b9e35030b71fd7 3da179069b32e2935630e1c2062354d0da20a6c416e50be794ca4y:c0b6e67b4ac098eb1a32c5f8c4c1f0e7e6fb9d832532e27d0bdab9ca2d2a8123ce5a8018b8161 a760480fadd040b927281ddb22cb9bc4df596d7de4d1b977d50Private key:Code View:p:fca682ce8e12caba26efccf7110e526db078b05edecbcd1eb4a208f3ae1617ae01f35b91a47e6df 63413c5e12ed0899bcd132acd50d99151bdc43ee737592e17q: 962eddcc369cba8ebb260ee6b6a126d9346e38c5g:678471b27a9cf44ee91a49c5147db1a9aaf244f05a434d6486931d2d14271b9e35030b71fd73 da179069b32e2935630e1c2062354d0da20a6c416e50be794ca4x: 146c09f881656cc6c51f27ea6c3a91b85ed1d70aIt is believed to be practically impossible to compute one key from the other. That is, even though everyone knows your public key, they can't compute your private key in your lifetime, no matter how many computing resources they have available.It might seem difficult to believe that nobody can compute the private key from the public keys, but nobody has ever found an algorithm to do this for the encryption algorithms that are in common use today. If the keys are sufficiently long, brute force—simply trying all possible keys—would require more computers than can be built from all the atoms in the solar system, crunching away for thousands of years. Of course, it is possible that someone could come up with algorithms for computing keys that are much more clever than brute force. For example, the RSA algorithm (the encryption algorithm invented by Rivest, Shamir, and Adleman) depends on the difficulty of factoring large numbers. For the last 20 years, many of the best mathematicians have tried to come up with good factoring algorithms, but so far with no success. For that reason, most cryptographers believe that keys with a "modulus" of 2,000 bits or more are currently completely safe from any attack. DSA is believed to be similarly secure.Figure 9-12 illustrates how the process works in practice.Suppose Alice wants to send Bob a message, and Bob wants to know this message came from Alice and not an impostor. Alice writes the message and then signs the message digest with her private key. Bob gets a copy of her public key. Bob then applies the public key to verify thesignature. If the verification passes, then Bob can be assured of two facts:•The original message has not been altered.•The message was signed by Alice, the holder of the private key that matches the public key that Bob used for verification.You can see why security for private keys is all-important. If someone steals Alice's private key or if a government can require her to turn it over, then she is in trouble. The thief or a government agent can impersonate her by sending messages, money transfer instructions, and so on, that others will believe came from Alice.The X.509 Certificate FormatTo take advantage of public key cryptography, the public keys must be distributed. One of the most common distribution formats is called X.509. Certificates in the X.509 format are widely used by VeriSign, Microsoft, Netscape, and many other companies, for signing e-mail messages, authenticating program code, and certifying many other kinds of data. The X.509 standard is part of the X.500 series of recommendations for a directory service by the international telephone standards body, the CCITT.The precise structure of X.509 certificates is described in a formal notation, called "abstract syntax notation #1" or ASN.1. Figure 9-13 shows the ASN.1 definition of version 3 of the X.509 format. The exact syntax is not important for us, but, as you can see, ASN.1 gives a precise definition of the structure of a certificate file. The basic encoding rules, or BER, and a variation, called distinguished encoding rules (DER) describe precisely how to save this structure in a binary file. That is, BER and DER describe how to encode integers, character strings, bit strings, and constructs such as SEQUENCE, CHOICE, and OPTIONAL.译文：Java核心技术卷Ⅱ高级特性当Java技术刚刚问世时，令人激动的并不是因为它是一个设计完美的编程语言，而是因为它能够安全地运行通过因特网传播的各种applet。
(完整word版)JAVA外文文献+翻译
Java and the InternetIf Java is, in fact， yet another computer programming language， you may question why it is so important and why it is being promoted as a revolutionary step in computer programming. The answer isn't immediately obvious if you’re comin g from a traditional programming perspective. Although Java is very useful for solving traditional stand—alone programming problems, it is also important because it will solve programming problems on the World Wide Web。
1.Client—side programmingThe Web’s in itial server—browser design provided for interactive content， but the interactivity was completely provided by the server. The server produced static pages for the client browser, which would simply interpret and display them。
Basic HTML contains simple mechanisms for data gathering: text-entry boxes， check boxes, radio boxes， lists and drop—down lists, as well as a button that can only be programmed to reset the data on the form or “submit” the data on the form back to the server。
JAVA外文翻译
英文原文:The Java programming language and platform have emerged as major technologies for performing e-business functions. Java programming standards have enabled portability of applications and the reuse of application components across computing platforms. Sun Microsystems' Java Community Process continues to be a strong base for the growth of the Java infrastructure and language standards. This growth of open standards creates new opportunities for designers and developers of applications and services .Applications of JavaJava uses many familiar programming concepts and constructs and allows portability by providing a common interface through an external Java Virtual Machine (JVM). A virtual machine is a self-contained operating environment, created by a software layer that behaves as if it were a separate computer. Benefits of creating virtual machines include better exploitation of powerful computing resources and isolation of applications to prevent cross-corruption and improve security.The JVM allows computing devices with limited processors or memory to handle more advanced applications by calling up software instructions inside the JVM to perform most of the work. This also reduces the size and complexity of Java applications because many of the core functions and processing instructions were built into the JVM. As a result, software developers no longer need to re-create the same application for every operating system. Java also provides security by instructing the application to interact with the virtual machine, which served as a barrier between applications and the core system, effectively protecting systems from malicious code.Among other things, Java is tailor-made for the growing Internet because it makes it easy to develop new, dynamic applications that could make the most of the Internet's power and capabilities. Java is now an open standard, meaning that no single entity controls its development and the tools for writing programs in the language are available to everyone. The power of open standards like Java is the ability to break down barriers and speed up progress.Today, you can find Java technology in networks and devices that range from the Internet and scientific supercomputers to laptops and cell phones, from Wall Street market simulators tohome game players and credit cards. There are over 3 million Java developers and now there are several versions of the code. Most large corporations have in-house Java developers. In addition, the majority of key software vendors use Java in their commercial applications (Lazaridis, 2003).ApplicationsJava on the World Wide WebJava has found a place on some of the most popular websites in the world and the uses of Java continues to grow. Java applications not only provide unique user interfaces, they also help to power the backend of websites. Everybody is probably familiar with eBay and Amazon have been Java pioneers on the World Wide Web.eBayFounded in 1995, eBay enables e-commerce on a local, national and international basis with an array of Web sites.You can find it on eBay, even if you didn't know it existed. On a typical day, more than 100 million items are listed on eBay in tens of thousands of categories. on eBay; the world's largest online marketplace.eBay uses Java almost everywhere. To address some security issues, eBay chose Sun Microsystems' Java System Identity Manager as the platform for revamping its identity management system. The task at hand was to provide identity management for more than 12,000 eBay employees and contractors.Now more than a thousand eBay software developers work daily with Java applications. Java's inherent portability allows eBay to move to new hardware to take advantage of new technology, packaging, or pricing, without having to rewrite Java code.Amazon has created a Web Service application that enables users to browse their product catalog and place orders. uses a Java application that searches the Amazon catalog for books whose subject matches a user-selected topic. The application displays ten books that match the chosen topic, and shows the author name, book title, list price, Amazon discount price, and the cover icon. The user may optionally view one review per displayed title and make a buying decision.Java in Data Warehousing & MiningAlthough many companies currently benefit from data warehousing to support corporatedecision making, new business intelligence approaches continue to emerge that can be powered by Java technology. Applications such as data warehousing, data mining, Enterprise Information Portals and Knowledge Management Systems are able to provide insight into customer retention, purchasing patterns, and even future buying behavior.These applications can not only tell what has happened but why and what may happen given certain business conditions; As a result of this information growth, people at all levels inside the enterprise, as well as suppliers, customers, and others in the value chain, are clamoring for subsets of the vast stores of information to help them make business decisions. While collecting and storing vast amounts of data is one thing, utilizing and deploying that data throughout the organization is another.The technical challenges inherent in integrating disparate data formats, platforms, and applications are significant. However, emerging standards such as the Application Programming Interfaces that comprise the Java platform, as well as Extendable Markup Language technologies can facilitate the interchange of data and the development of next generation data warehousing and business intelligence applications. While Java technology has been used extensively for client side access and to presentation layer challenges, it is rapidly emerging as a significant tool for developing scaleable server side programs. The Java2 Platform, Enterprise Edition (J2EE) provides the object, transaction, and security support for building such systems.Metadata IssuesOne of the key issues that business intelligence developers must solve is that of incompatible metadata formats. Metadata can be defined as information about data or simply "data about data." In practice, metadata is what most tools, databases, applications, and other information processes use to define, relate, and manipulate data objects within their own environments. It defines the structure and meaning of data objects managed by an application so that the application knows how to process requests or jobs involving those data objects. Developers can use this schema to create views for users. Also, users can browse the schema to better understand the structure and function of the database tables before launching a query.To address the metadata issue, a group of companies have joined to develop the Java Metadata Interface (JMI) API. The JMI API permits the access and manipulation of metadata in Java with standard metadata services. JMI is based on the Meta Object Facility (MOF)specification from the Object Management Group (OMG). The MOF provides a model and a set of interfaces for the creation, storage, access, Metamodel and metadata interchange is done via XML and uses the XML Metadata Interchange (XMI) specification, also from the OMG. JMI leverages Java technology to create an end-to-end data warehousing and business intelligence solutions framework.Enterprise JavaBeansA key tool provided by J2EE is Enterprise JavaBeans (EJB), an architecture for the development of component-based distributed business applications. Applications written using the EJB architecture are scalable, transactional, secure, and multi-user aware. These applications may be written once and then deployed on any server platform that supports J2EE. The EJB architecture makes it easy for developers to write components, since they do not need to understand or deal with complex, system-level details such as thread management, resource pooling, and transaction and security management. This allows for role-based development where component assemblers, platform providers and application assemblers can focus on their area of responsibility further simplifying application development.Data Storage & AccessData stored in existing applications can be accessed with specialized connectors. Integration and interoperability of these data sources is further enabled by the metadata repository that contains metamodels of the data contained in the sources, which then can be accessed and interchanged uniformly via the JMI API. These metamodels capture the essential structure and semantics of business components, allowing them to be accessed and queried via the JMI API or to be interchanged via XML. Through all of these processes, the J2EE infrastructure ensures the security and integrity of the data through transaction management and propagation and the underlying security architecture.To consolidate historical information for analysis of sales and marketing trends, a data warehouse is often the best solution. In this example, data can be extracted from the operational systems with a variety of Extract, Transform and Load tools (ETL). The metamodels allow EJBs designed for filtering, transformation, and consolidation of data to operate uniformly on data from diverse data sources as the bean is able to query the metamodel to identify and extract the pertinent fields. Queries and reports can be run against the data warehouse that containsinformation from numerous sources in a consistent, enterprise-wide fashion through the use of the JMI API.Java in Industrial SettingsMany people know Java only as a tool on the World Wide Web that enables sites to perform some of their fancier functions such as interactivity and animation. However, the actual uses for Java are much more widespread. Since Java is an object-oriented language, the time needed for application development is minimal.In addition, Java's automatic memory management and lack of pointers remove some leading causes of programming errors. Most importantly, application developers do not need to create different versions of the software for different platforms. The advantages available through Java have even found their way into hardware. The emerging new Java devices are streamlined systems that exploit network servers for much of their processing power, storage, content, and administration.Benefits of JavaThe benefits of Java translate across many industries, and some are specific to the control and automation environment. Java's ability to run on any platform enables the organization to make use of the existing equipment while enhancing the application.IntegrationWith few exceptions, applications running on the factory floor were never intended to exchange information with systems in the executive office, but managers have recently discovered the need for that type of information. Before Java, that often meant bringing together data from systems written on different platforms in different languages at different times. Integration was usually done on a piecemeal basis, once it worked, was unique to the two applications it was tying together. Additional integration required developing a brand new system from scratch, raising the cost of integration.ScalabilityAnother benefit of Java in the industrial environment is its scalability. Even when internal compatibility is not an issue, companies often face difficulties when suppliers with whom they share information have incompatible systems. This becomes more of a problem as supply-chain management takes on a more critical role which requires manufacturers to interact more withoffshore suppliers and clients. The greatest efficiency comes when all systems can communicate with each other and share information seamlessly. Since Java is so ubiquitous, it often solves these problems.Dynamic Web Page DevelopmentJava has been used by both large and small organizations for a wide variety of applications beyond consumer oriented websites. Sandia, a multiprogram laboratory of the U.S. Department of Energy's National Nuclear Security Administration, has developed a unique Java application. The lab was tasked with developing an enterprise-wide inventory tracking and equipment maintenance system that provides dynamic Web pages.ConclusionOpen standards have driven the e-business revolution. As e-business continues to develop, various computing technologies help to drive its evolution. The Java programming language and platform have emerged as major technologies for performing e-business functions. the time needed for application development is minimal. Java also encourages good software engineering practices with clear separation of interfaces and implementations as well as easy exception handling. Java's automatic memory management and lack of pointers remove some leading causes of programming errors. The advantages available through Java have also found their way into hardware. The emerging new Java devices are streamlined systems that exploit network servers for much of their processing power, storage, content, and administration.中文翻译:Java编程语言和Java平台，已成为主要的实现电子商务功能的技术。
Java调用翻译软件实现英文文档翻译
Java调⽤翻译软件实现英⽂⽂档翻译前⾔：因最近要进⾏OCP的考试准备。
看着⼤堆英⽂⽂档确实有些疼痛。
⼜因⽂档内容有点⼤，⼜需要逐⼀去翻译⼜很费时费⼒。
于是百度了⼀番，找到⼀些可以使⽤Java来调⽤百度翻译软件的API（注：（官⽅标注）每⽉前200万字不要钱，49元/⽉）。
于是就⾃⼰⼿动的修改了⼀番。
然后就使⽤。
Java调⽤百度API实现翻译百度官⽅计费声明：下⾯是Java调⽤百度API实现翻译的具体步骤：⼀、在写代码之前先在在百度翻译平台中，申请APP_ID申请地址申请的详见申请之后，会得到APP_ID和SECURITY_KEY⼆、java代码如下1：代码结构下图2：主要代码如下：BaiduTranslateDemopackage spring;import java.io.BufferedReader;import java.io.InputStream;import java.io.InputStreamReader;import .URLDecoder;import java.util.ArrayList;import java.util.List;import java.util.Random;import mons.codec.digest.DigestUtils;import org.apache.http.Consts;import org.apache.http.HttpEntity;import ValuePair;import org.apache.http.client.entity.UrlEncodedFormEntity;import org.apache.http.client.methods.CloseableHttpResponse;import org.apache.http.client.methods.HttpPost;import org.apache.http.impl.client.CloseableHttpClient;import org.apache.http.impl.client.HttpClients;import org.apache.http.message.BasicNameValuePair;import org.json.JSONArray;import org.json.JSONObject;import org.springframework.context.ApplicationContext;import org.springframework.context.support.FileSystemXmlApplicationContext;/*** 百度翻译引擎java⽰例代码*/public class BaiduTranslateDemo{private static final String UTF8 = "utf-8";//申请者开发者id，实际使⽤时请修改成开发者⾃⼰的appidprivate static final String appId = "⾃⼰注册⼀个appid";//申请成功后的证书token，实际使⽤时请修改成开发者⾃⼰的tokenprivate static final String token = "认证证书信息";private static final String url = "/api/trans/vip/translate";//随机数，⽤于⽣成md5值，开发者使⽤时请激活下边第四⾏代码private static final Random random = new Random();public String translate(String q, String from, String to) throws Exception{//⽤于md5加密//int salt = random.nextInt(10000);//本演⽰使⽤指定的随机数为1435660288int salt = 1435660288;// 对appId+源⽂+随机数+token计算md5值StringBuilder md5String = new StringBuilder();md5String.append(appId).append(q).append(salt).append(token);String md5 = DigestUtils.md5Hex(md5String.toString());//使⽤Post⽅式，组装参数HttpPost httpost = new HttpPost(url);List<NameValuePair> nvps = new ArrayList<NameValuePair>();nvps.add(new BasicNameValuePair("q", q));nvps.add(new BasicNameValuePair("from", from));nvps.add(new BasicNameValuePair("to", to));nvps.add(new BasicNameValuePair("appid", appId));nvps.add(new BasicNameValuePair("salt", String.valueOf(salt)));nvps.add(new BasicNameValuePair("sign", md5));httpost.setEntity(new UrlEncodedFormEntity(nvps, Consts.UTF_8));//创建httpclient链接，并执⾏CloseableHttpClient httpclient = HttpClients.createDefault();CloseableHttpResponse response = httpclient.execute(httpost);//对于返回实体进⾏解析HttpEntity entity = response.getEntity();InputStream returnStream = entity.getContent();BufferedReader reader = new BufferedReader(new InputStreamReader(returnStream, UTF8));StringBuilder result = new StringBuilder();String str = null;while ((str = reader.readLine()) != null) {result.append(str).append("\n");}//转化为json对象，注：Json解析的jar包可选其它JSONObject resultJson = new JSONObject(result.toString());//开发者⾃⾏处理错误，本⽰例失败返回为nulltry {String error_code = resultJson.getString("error_code");if (error_code != null) {System.out.println("出错代码:" + error_code);System.out.println("出错信息:" + resultJson.getString("error_msg"));return null;}} catch (Exception e) {}//获取返回翻译结果JSONArray array = (JSONArray) resultJson.get("trans_result");JSONObject dst = (JSONObject) array.get(0);String text = dst.getString("dst");text = URLDecoder.decode(text, UTF8);return text;}/*** 实际抛出异常由开发者⾃⼰处理中⽂翻译英⽂* @param q* @return* @throws Exception*/public static String translateZhToEn(String q) throws Exception{ApplicationContext container=new FileSystemXmlApplicationContext("src//spring//resource//baidu.xml"); BaiduTranslateDemo baidu = (BaiduTranslateDemo)container.getBean("baidu");String result = null;try {result = baidu.translate(q, "zh", "en");} catch (Exception e) {e.printStackTrace();}return result;}/*** 实际抛出异常由开发者⾃⼰处理英⽂翻译中⽂* @param q* @return* @throws Exception*/public static String translateEnToZh(String q) throws Exception{ApplicationContext container=new FileSystemXmlApplicationContext("src//spring//resource//baidu.xml"); BaiduTranslateDemo baidu = (BaiduTranslateDemo)container.getBean("baidu");String result = null;try {result = baidu.translate(q, "en", "zh");} catch (Exception e) {e.printStackTrace();}return result;}}Mainpackage spring;import java.io.BufferedReader;import java.io.BufferedWriter;import java.io.File;import java.io.FileOutputStream;import java.io.FileReader;import java.io.FileWriter;import java.io.OutputStream;import java.io.OutputStreamWriter;/*** 直接运⾏main⽅法即可输出翻译结果*/public class Main {public static void main(String[] args) throws Exception {// translateZhToEn();// translateEnToZh();translateTxtInfo();}/*** 中⽂翻译为英⽂*/public static void translateZhToEn() {String source = "百度翻译引擎⽰例";String result;try {result = BaiduTranslateDemo.translateZhToEn(source);if (result == null) {System.out.println("翻译出错，参考百度错误代码和说明。
java实现英文翻译程序
java实现英⽂翻译程序本⽂实例为⼤家分享了java实现英⽂翻译程序的具体代码，供⼤家参考，具体内容如下1.功能简介将⽂本⽂件中的英⽂转换为对应的中⽂词库如下：源⽂件：翻译后的⽂件：输⼊源⽂件路径，将翻译后的内容输出到result.txt⽂件中。
2.重要技术（1）如何载⼊词库⽂件因为词库⽂件是 kry=value的形式，所有可以⽤到Properties类的load函数（2）如何将源⽂件中的⼀段英⽂分理处⼀个个的单词可以⽤StringTokenizer类（3）如何进⾏翻译直接⽤中⽂替换相应的英⽂3.项⽬结构（4）代码编写①FileLoader类/*⽂件载⼊类，将源⽂件中的内容输出到字节数组中*/package zhidao3_2;import java.io.FileInputStream;import java.io.File;public class FileLoad {public static byte[] getContent(String fileName)throws Exception{File file = new File(fileName);if(!file.exists()){System.out.println("输⼊有误，该⽂件不存在");}FileInputStream fis = new FileInputStream(file);int length = (int)file.length();byte[] data = new byte[length];fis.read(data);fis.close();return data;}}②TxtTrans类/*⽂件翻译，将字节数组变为字符串，分离出其中的单词，然后翻译为对应的汉字，去掉空格，变为字符串*/ package zhidao3_2;import java.util.StringTokenizer;import java.util.Properties;import java.io.*;public class TxtTrans {private Properties pps;public TxtTrans(){loadCiku();}public void loadCiku(){pps = new Properties();try{FileReader fis = new FileReader("g:/ciku.txt");//以字符载⼊时没有乱码，以字节载⼊时出现了乱码pps.load(fis);fis.close();}catch(Exception ex){ex.printStackTrace(System.out);System.out.println("载⼊词库时出错");}//System.out.println(pps.get("china")) ;}public String trans(byte[] data){String srcTxt = new String(data);String dstTxt = srcTxt;String delim = " ,.!\n\t"; //分隔符可以指定StringTokenizer st = new StringTokenizer(srcTxt,delim,false);String sub,lowerSub,newSub;//int i=0;while(st.hasMoreTokens()){sub = st.nextToken(); //分割出的⼀个个单词lowerSub = sub.toLowerCase();//统⼀转换为⼩写，这样可以简化词库//System.out.println(sub);newSub = pps.getProperty(lowerSub);if(newSub != null){ //如果找到了匹配的汉字，则进⾏替换dstTxt = dstTxt.replaceFirst(sub, newSub); //只替换第⼀个，即只替换了当前的字符串，否则容易造成ch我na的例⼦ //System.out.println(dstTxt);}}return dstTxt.replaceAll(" ", ""); //去掉空格}}③FileOutput类/*将字符串输出到⽂件*/package zhidao3_2;import java.io.File;import java.io.FileOutputStream;public class FileOutput {public static void output(String text,String fileName)throws Exception{File file = new File(fileName);FileOutputStream fos = new FileOutputStream(file);fos.write(text.getBytes());fos.close();}}④主函数package zhidao3_2;import javax.swing.JOptionPane;public class Main {public static void main(String[] args) {String srcFile = JOptionPane.showInputDialog("输⼊源⽂件");try{byte[] data = FileLoad.getContent(srcFile);TxtTrans tt = new TxtTrans();String dString = tt.trans(data);FileOutput.output(dString, "g:/result.txt");}catch(Exception ex){JOptionPane.showMessageDialog(null, "操作异常");System.exit(1);}JOptionPane.showMessageDialog(null, "翻译完毕");}}最后的项⽬结构如下：以上就是本⽂的全部内容，希望对⼤家的学习有所帮助，也希望⼤家多多⽀持。
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毕业设计外文资料翻译（译文）题目名称：Java and the Internet学院：计算机科学技术专业年级：计算机科学与技术（师）08 级学生姓名：aaa班级学号：a班a号指导教师：aaa二○一一年五月十三日译文题目：Java和因特网原文题目：Java and the Internet原文出处：/view.htmlJava and the InternetIf Java is, in fact, yet another computer programming language, you may question why it is so important and why it is being promoted as a revolutionary step in computer programming. The answer isn’t immediately obvious if you’re coming from a traditional programming perspective. Although Java is very useful for solving traditional stand-alone programming problems, it is also important because it will solve programming problems on the World Wide Web.1.Client-side programmingThe Web’s initial server-browser design provided for interactive content, but the interactivity was completely provided by the server. The server produced static pages for the client browser, which would simply interpret and display them. Basic HTML contains simple mechanisms for data gathering: text-entry boxes, check boxes, radio boxes, lists and drop-down lists, as well as a button that can only be programmed to reset the data on the form or “submit” the data on the form back to the server. This submission passes through the Common Gateway Interface (CGI) provided on all Web servers. The text within the submission tells CGI what to do with it. The most common action is to run a program located on the server in a directory that’s typically called “cgi-bin.” (If you watch the address window at the top of your browser when you push a button on a Web page, you can so metimes see “cgi-bin” within all the gobbledygook there.) These programs can be written in most languages. Perl is a common choice because it is designed for text manipulation and is interpreted, so it can be installed on any server regardless of processor or operating system.Many powerful Web sites today are built strictly on CGI, and you can in fact do nearly anything with it. However, Web sites built on CGI programs can rapidly become overly complicated to maintain, and there is also the problem of response time. The response of a CGI program depends on how much data must be sent, as well as the load on both the server and the Internet. (On top of this, starting a CGI program tends to be slow.) The initial designers of the Web did not foresee how rapidly this bandwidth would be exhausted for the kinds of applications people developed. For example, any sort of dynamic graphing is nearly impossible to perform with consistency because a GIF file must be created and moved from the server to the client for eac h version of the graph. And you’ve no doubt had direct experience with something as simple as validating the data on an input form. You press the submit button on a page; the data is shipped back to the server; the server starts a CGI program that discovers an error, formats an HTML page informing you of the error, and then sends the page back to you; you must then back up a page and try again. Not only is this slow, it’s inelegant.The solution is client-side programming. Most machines that run Web browsers are powerful engines capable of doing vast work, and with the original static HTMLapproach they are sitting there, just idly waiting for the server to dish up the next page. Client-side programming means that the Web browser is harnessed to do whatever work it can, and the result for the user is a much speedier and more interactive experience at your Web site.The problem with discussions of client-side programming is that they aren’t very different from discussions of programming in general. The parameters are almost the same, but the platform is different: a Web browser is like a limited operating system. In the end, you must still program, and this accounts for the dizzying array of problems and solutions produced by client-side programming. The rest of this section provides an overview of the issues and approaches in client-side programming.2.Plug-insOne of the most significant steps forward in client-side programming is the development of the plug-in. This is a way for a programmer to add new functionality to the browser by downloading a piece of code that plugs itself into the appropriate spot in the browser. It tells the browser “from now on you can perform this new activity.” (You need to download the plug-in only once.) Some fast and powerful behavior is added to browsers via plug-ins, but writing a plug-in is not a trivial task, and isn’t something you’d want to do as part of the process of building a particular site. The value of the plug-in for client-side programming is that it allows an expert programmer to develop a new language and add that language to a browser without the permission of the browser manufacturer. Thus, plug-ins provide a “back door” that allows the creation of new client-side programming languages (although not all languages are implemented as plug-ins).3.Scripting languagesPlug-ins resulted in an explosion of scripting languages. With a scripting language you embed the source code for your client-side program directly into the HTML page, and the plug-in that interprets that language is automatically activated while the HTML page is being displayed. Scripting languages tend to be reasonably easy to understand and, because they are simply text that is part of an HTML page, they load very quickly as part of the single server hit required to procure that page. The trade-off is that your code is exposed for everyone to see (and steal). Generally, however, you aren’t doing amazingly sophisticated things with scripting languages so this is not too much of a hardship.This points out that the scripting languages used inside Web browsers are really intended to solve specific types of problems, primarily the creation of richer and more interactive graphical user interfaces (GUIs). However, a scripting language might solve 80 percent of the problems encountered in client-side programming. Your problems might very well fit completely within that 80 percent, and since scripting languages can allow easier and faster development, you should probably consider ascripting language before looking at a more involved solution such as Java or ActiveX programming.The most commonly discussed browser scripting languages are JavaScript (which has nothing to do with Java; it’s named that way just to grab some of Java’s marketing momentum), VBScript (which looks like Visual Basic), and Tcl/Tk, which comes from the popular cross-platform GUI-building language. There are others out there, and no doubt more in development.JavaScript is probably the most commonly supported. It comes built into both Netscape Navigator and the Microsoft Internet Explorer (IE). In addition, there are probably more JavaScript books available than there are for the other browser languages, and some tools automatically create pages using JavaScript. However, if you’re already fluent in Visual Basic or Tcl/Tk, you’ll be more productive using those scripting languages rather than learning a new one. (You’ll have your hands full dealing with the Web issues already.)4.JavaIf a scripting language can solve 80 percent of the client-side programming problems, what about the other 20 percent—the “really hard stuff?” The most popular solution today is Java. Not only is it a powerful programming language built to be secure, cross-platform, and international, but Java is being continually extended to provide language features and libraries that elegantly handle problems that are difficult in traditional programming languages, such as multithreading, database access, network programming, and distributed computing. Java allows client-side programming via the applet.An applet is a mini-program that will run only under a Web browser. The applet is downloaded automatically as part of a Web page (just as, for example, a graphic is automatically downloaded). When the applet is activated it executes a program. This is part of its beauty—it provides you with a way to automatically distribute the client software from the server at the time the user needs the client software, and no sooner. The user gets the latest version of the client software without fail and without difficult reinstallation. Because of the way Java is designed, the programmer needs to create only a single program, and that program automatically works with all computers that have browsers with built-in Java interpreters. (This safely includes the vast majority of machines.) Since Java is a full-fledged programming language, you can do as much work as possible on the client before and after making requests of the server. For example, you won’t need to send a request form across the Inte rnet to discover that you’ve gotten a date or some other parameter wrong, and your client computer can quickly do the work of plotting data instead of waiting for the server to make a plot and ship a graphic image back to you. Not only do you get the immediate win of speed and responsiveness, but the general network traffic and load on servers can be reduced, preventing the entire Internet from slowing down.One advantage a Java applet has over a scripted program is that it’s in compiled form, so the source code isn’t available to the client. On the other hand, a Java appletcan be decompiled without too much trouble, but hiding your code is often not an important issue. Two other factors can be important. As you will see later in this book, a compiled Java applet can comprise many modules and take multiple server “hits” (accesses) to download. (In Java 1.1 and higher this is minimized by Java archives, called JAR files, that allow all the required modules to be packaged together and compressed for a single download.) A scripted program will just be integrated into the Web page as part of its text (and will generally be smaller and reduce server hits). This could be important to the responsiveness of your Web site. Another factor is the all-important learning curve. Regardless of what you’ve heard, Java is not a trivial language to learn. If you’re a Visual Basic programmer, moving to VBScript will be your fastest solution, and since it will probably solve most typical client/server problems you might be hard p ressed to justify learning Java. If you’re experienced with a scripting language you will certainly benefit from looking at JavaScript or VBScript before committing to Java, since they might fit your needs handily and you’ll be more productive sooner.to ru n its applets withi5.ActiveXTo some degree, the competitor to Java is Microsoft’s ActiveX, although it takes a completely different approach. ActiveX was originally a Windows-only solution, although it is now being developed via an independent consortium to become cross-platform. Effectively, ActiveX says “if your program connects to its environment just so, it can be dropped into a Web page and run under a browser that supports ActiveX.” (IE directly supports ActiveX and Netscape does so using a plug-in.) Thus, ActiveX does not constrain you to a particular language. If, for example, you’re already an experienced Windows programmer using a language such as C++, Visual Basic, or Borland’s Delphi, you can create ActiveX components with almost no changes to your programming knowledge. ActiveX also provides a path for the use of legacy code in your Web pages.6.SecurityAutomatically downloading and running programs across the Internet can sound like a virus-builder’s dream. ActiveX especially brings up the th orny issue of security in client-side programming. If you click on a Web site, you might automatically download any number of things along with the HTML page: GIF files, script code, compiled Java code, and ActiveX components. Some of these are benign; GIF files can’t do any harm, and scripting languages are generally limited in what they can do. Java was also designed to run its applets within a “sandbox” of safety, which prevents it from writing to disk or accessing memory outside the sandbox.ActiveX is at the opposite end of the spectrum. Programming with ActiveX is like programming Windows—you can do anything you want. So if you click on a page that downloads an ActiveX component, that component might cause damage to thefiles on your disk. Of course, programs that you load onto your computer that are not restricted to running inside a Web browser can do the same thing. Viruses downloaded from Bulletin-Board Systems (BBSs) have long been a problem, but the speed of the Internet amplifies the difficulty.The solution seems to be “digital signatures,” whereby code is verified to show who the author is. This is based on the idea that a virus works because its creator can be anonymous, so if you remove the anonymity individuals will be forced to be responsible for their actions. This seems like a good plan because it allows programs to be much more functional, and I suspect it will eliminate malicious mischief. If, however, a program has an unintentional destructive bug it will still cause problems. The Java approach is to prevent these problems from occurring, via the sandbox. The Java interpreter that lives on your local Web browser examines the applet for any untoward instructions as the applet is being loaded. In particular, the applet cannot write files to disk or erase files (one of the mainstays of viruses). Applets are generally considered to be safe, and since this is essential for reliable client/server systems, any bugs in the Java language that allow viruses are rapidly repaired. (It’s worth noting that the browser software actually enforces these security restrictions, and some browsers allow you to select different security levels to provide varying degrees of access to your system.)You might be skeptical of this rather draconian restriction against writing files to your local disk. For example, you may want to build a local database or save data for later use offline. The initial vision seemed to be that eventually everyone would get online to do anything important, but that was soon seen to be impractical (although low-cost “Internet appliances” might someday satisfy the needs of a significant segment of users). The solution is the “signed applet” that uses public-key encryption to verify that an applet does indeed come from where it claims it does. A signed applet can still trash your disk, but the theory is that since you can now hold the applet creator accountable they won’t do vicious things. Java provides a framework for digital signatures so that you will eventually be able to allow an applet to step outside the sandbox if necessary.Digital signatures have missed an important issue, which is the speed that people move around on the Internet. If you download a buggy program and it does something untoward, how long will it be before you discover the damage? It could be days or even weeks. By then, how will you track down the program that’s done it? And what good will it do you at that point?7.Internet vs. intranetreferred to as an intranet. Intranets provide much greater security than the Internet, since you can p The Web is the most general solution to the client/server problem, so it makes sense that you can use the same technology to solve a subset of the problem, in particular the classic client/server problem within a company. With traditional client/server approaches you have the problem of multiple types of client computers, as well as the difficulty of installing new client software, both of which are handilysolved with Web browsers and client-side programming. When Web technology is used for an information network that is restricted to a particular company, it is hysically control access to the servers within your company. In terms of training, it seems that once people understand the general concept of a browser it’s much easier for them to deal with differences in the way pages and applets look, so the learning curve for new kinds of systems seems to be reduced.The security problem brings us to one of the divisions that seems to be automatically forming in the world of client-side programming. If your program is running on the Internet, you don’t know what platform it will be working under, and you want to be extra careful that you don’t disseminate buggy code. You need something cross-platform and secure, like a scripting language or Java.If you’re running on an intranet, you might have a different set of constraints. It’s not uncommon that your machines could all be Intel/Windows platforms. On an intranet, you’re responsible for the quality of your own code and can repair bugs when they’re discovered. In addition, you might already have a body of legacy code that you’ve been using in a more traditional client/server approach, whereby you must physically install client programs every time you do an upgrade. The time wasted in installing upgrades is the most compelling reason to move to browsers, because upgrades are invisible and automatic. If you are involved in such an intranet, the most sensible approach to take is the shortest path that allows you to use your existing code base, rather than trying to recode your programs in a new language.When faced with this bewildering array of solutions to the client-side programming problem, the best plan of attack is a cost-benefit analysis. Consider the constraints of your problem and what would be the shortest path to your solution. Since client-side programming is still programming, it’s always a good idea to take the fastest development approach for your particular situation. This is an aggressive stance to prepare for inevitable encounters with the problems of program development.8.Server-side programmingThis whole discussion has ignored the issue of server-side programming. What happens when you make a request of a server? Most of the time the request is simply “send me this file.” Your browser then interprets the file in some appropriate fashion: as an HTML page, a graphic image, a Java applet, a script program, etc. A more complicated request to a server generally involves a database transaction. A common scenario involves a request for a complex database search, which the server then formats into an HTML page and sends to you as the result. (Of course, if the client has more intelligence via Java or a scripting language, the raw data can be sent and formatted at the client end, which will be faster and less load on the server.) Or you might want to register your name in a database when you join a group or place an order, which will involve changes to that database. These database requests must be processed via some code on the server side, which is generally referred to as server-side programming. Traditionally, server-side programming has been performed using Perl and CGI scripts, but more sophisticated systems have been appearing.These include Java-based Web servers that allow you to perform all your server-side programming in Java by writing what are called servlets. Servlets and their offspring, JSPs, are two of the most compelling reasons that companies who develop Web sites are moving to Java, especially because they eliminate the problems of dealing with differently abled browsers.9. separate arena: applicationsMuch of the brouhaha over Java has been over applets. Java is actually a general-purpose programming language that can solve any type of problem—at least in theory. And as pointed out previously, there might be more effective ways to solve most client/server problems. When you move out of the applet arena (and simultaneously release the restrictions, such as the one against writing to disk) you enter the world of general-purpose applications that run standalone, without a Web browser, just like any ordinary program does. Here, Java’s strength is not only in its portability, but also its programmability. As you’ll see throughout this book, Java has many features that allow you to create robust programs in a shorter period than with previous programming languages.Be aware that this is a mixed blessing. You pay for the improvements through slower execution speed (although there is significant work going on in this area—JDK 1.3, in particular, introduces the so-called “hotspot” performance improvements). Like any language, Java has built-in limitations that might make it inappropriate to solve certain types of programming problems. Java is a rapidly evolving language, however, and as each new release comes out it becomes more and more attractive for solving larger sets of problems.Java和因特网既然Java不过另一种类型的程序设计语言，大家可能会奇怪它为什么值得如此重视，为什么还有这么多的人认为它是计算机程序设计的一个里程碑呢？如果您来自一个传统的程序设计背景，那么答案在刚开始的时候并不是很明显。