考试酷java 第二章

合集下载

Java入门经典第2章动手写Hello World知识点练习答案及课后习题答案

第2章动手写“Hello World”并不是每台计算机都可以运行Java程序，要运行Java程序，计算机必须搭建Java开发环境，而编写Java程序则可以使用任何的文本编辑工具，如最简单的文本编辑工具之一——记事本。

搭建Java开发环境是每一位Java程序员必须掌握并熟练使用的一项技能。

本章为大家介绍接触Java的第一步——搭建Java开发环境。

知识点：1、并不是每台计算机都可以运行Java程序，要运行Java程序，计算机必须搭建Java开发环境，而编写Java程序则可以使用任何的文本编辑工具，如最简单的文本编辑工具之一——记事本。

练习：1、并不是每台计算机都可以运行Java程序，要运行Java程序，计算机必须搭建，而编写Java程序则可以使用任何的，如最简单的文本编辑工具之一—— 。

通过本章的学习，希望读者可以达到以下的学习目的：□ 学会下载JDK。

□ 掌握如何安装JDK。

□ 掌握如何在Windows系统下配置和测试JDK。

□ 学会使用记事本编写Java程序。

□ 学会编译和运行Java程序。

2.1 搭建Java开发环境所谓“工欲善其事，必先利其器”，在学习一门语言之前，首先需要把整个开发环境搭建好。

要编译和执行Java程序，JDK是必备的。

下面将具体介绍下载并安装JDK及配置环境变量的方法。

2.1.2 下载JDK由于Sun公司已经被Oracle收购，因此JDK可以在Oracle公司的官方网站（/index.html）下载。

下面以目前最新版本JDK 7 Update 3为例介绍下载JDK的方法，具体下载步骤如下。

Step(1)打开IE浏览器，在地址栏中输入Oracle公司网站地址“/index.html”，并按下<Enter>键，进入到图2.1所示的Oracle官方网站主页面。

单击Oracle主页中的“Downloads”选项卡，然后在“Popular Downloads”栏目中单击“Java for Developers”超链接，这样就进入到Java SE相关资源下载页面。

java语言程序设计第二章编程练习题（1-11）

2.1import java.util.Scanner;public class eserciseII1{public static void main(String[] args){double F;//华氏温度值double C;//摄氏温度值//创建输入Scanner input=new Scanner(System.in);System.out.println("请输入摄氏温度值：\n");//控制台打印API//引入控制台输入C=input.nextDouble();System.out.println("华氏温度值为：\n");//控制台打印APISystem.out.println(F=((double)9/5)*C+32);//控制台打印API}}--------------------------------------------------------------------------------------------------------------------------------- 2.2import java.util.Scanner;/** 读入圆柱半径和高，并计算其体积；* 圆柱体积= 底面积* 高* 底面积= 半径*半径*PI（约为3.14）*/public class exerciseII2{public static void main(String[] args){final double PI=3.14;double R , H , V;//创建R输入Scanner inputR=new Scanner(System.in);System.out.println("输入半径:");//控制台打印APIR=inputR.nextDouble();///创建H输入Scanner inputH=new Scanner(System.in);System.out.println("输入圆柱高:");//控制台打印APIH=inputH.nextDouble();V=H*R*R*PI;System.out.println("圆柱体积为:"+V);//控制台打印API}}---------------------------------------------------------------------------------------------------------------------------------2.3import java.util.Scanner;/** 英尺与米的换算* 1英尺=0.305米*/public class exerciseII3{public static void main(String[] args){//创建输入Scanner input=new Scanner(System.in);System.out.println("输入英尺数");//控制台打印APIdouble 英尺=input.nextDouble();double 米=英尺*0.305;System.out.println(米);//控制台打印API}}---------------------------------------------------------------------------------------------------------------------------------2.4import java.util.Scanner;/** 将磅转换为千克* 1磅=0.454千克*/public class exerciseII4{public static void main(String[] args){//创建输入；Scanner input=new Scanner(System.in);System.out.println("输入磅数:\n");//控制台打印APIdouble 磅数=input.nextDouble();double 千克=磅数*0.454;System.out.println(千克);//控制台打印API}}---------------------------------------------------------------------------------------------------------------------------------2.5import java.util.Scanner;/** 总费用=费用*（1+酬金率）*/public class exerciseII5{public static void main(String[] args){//创建费用输入Scanner input费用=new Scanner(System.in);System.out.println("输入费用:\n");//控制台打印APIdouble 费用=input费用.nextDouble();//创建酬金率输入Scanner input酬金率=new Scanner(System.in);System.out.println("输入酬金率，例如15%输入15:\n");//控制台打印APIdouble 酬金率=input酬金率.nextDouble();double 总费用=费用*(1+酬金率/100);System.out.println(总费用);//控制台打印API}}--------------------------------------------------------------------------------------------------------------------------------- 2.6import java.util.Scanner;/** 一个数（0,100），并计算各个位置和*/public class exerciseII6{public static void main(String[] args){//创建输入Scanner input=new Scanner(System.in);System.out.println("输入一个数（0,1000）:\n");//控制台打印APIint 数=input.nextInt();int 个位,百位,千位,余,加和;千位=数/100;余=数%100;百位=余/10;余=余%10;个位=余;加和=个位+百位+千位;System.out.println(加和);//控制台打印API}}--------------------------------------------------------------------------------------------------------------------------------- 2.7import java.util.Scanner;public class exerciseII7{public static void main(String[] args){//创建输入Scanner input=new Scanner(System.in);System.out.println("输入分钟数:\n");//控制台打印APIdouble M=input.nextDouble();double tian=M/(60*24);System.out.println(tian);//控制台打印APIdouble nian=tian/365;System.out.println(nian);//控制台打印API}}--------------------------------------------------------------------------------------------------------------------------------- 2.8import java.util.Scanner;public class exerciseII8{public static void main(String[] args){//创建输入Scanner input=new Scanner(System.in);System.out.println("输入ASCII值:\n");//控制台打印APIint num=input.nextInt();char ch=(char)num;System.out.println(ch);//控制台打印API}}--------------------------------------------------------------------------------------------------------------------------------- 2.9import java.util.Scanner;public class exerciseII9{public static void main(String[] args){//创建输入Scanner input = new Scanner(System.in);System.out.println("输入数值，例如：$11.56:\n");//控制台打印APIdouble shu=input.nextDouble();int num=(int)(shu*100);int yuan=num/100;int yu=num%100;System.out.println("你输入的是"+yuan+"元"+yu+"分");//控制台打印API }}--------------------------------------------------------------------------------------------------------------------------------- 2.10import javax.swing.JOptionPane;public class exerciseII10{public static void main(String[] args){//创建对话框输入；String input = JOptionPane.showInputDialog("Enter an number of double");//String向其它类型转换；double 双= Double.parseDouble(input);//创建输出字符串；String output = "输出" + 双;//创建对话框输出；JOptionPane.showMessageDialog(null, output);}}--------------------------------------------------------------------------------------------------------------------------------- 2.11（对话框输入输出）import javax.swing.JOptionPane;public class exerciseII11控制台{public static void main(String[] args){//创建对话框输入String input = JOptionPane.showInputDialog("请输入姓名");String input1= JOptionPane.showInputDialog("请输入工作时间，例如：30");String input2= JOptionPane.showInputDialog("请输入工资，例如：2000000.1");String input3= JOptionPane.showInputDialog("请输入联邦所得税率，例如：1.2%输入12");String input4= JOptionPane.showInputDialog("请输入州所得税率，例如：1.2%输入12");//String向其它类型转换,如果本身就是字符串型的变量，直接用String input = JOptionPane.showInputDialog("请输入姓名\n");中的input即可；int 工作时间= Integer.parseInt(input1);double 工资= Double.parseDouble(input2);double 联邦所得税率= Double.parseDouble(input3);double 州所得税率=Double.parseDouble(input4);//创建输出字符串；String output ="姓名:\n"+input+"\n工作时间:\n"+工作时间+"\n工资:\n"+工资+"\n联邦所得税率:\n"+联邦所得税率+"%"+"\n州所得税率:\n"+州所得税率+"%";//创建对话框输出；JOptionPane.showMessageDialog(null, output);}}--------------------------------------------------------------------------------------------------------------------------------- 2.11(控制台输入，输出)import java.util.Scanner;public class exerciseII11对话框{public static void main(String[] args){//创建姓名输入Scanner input= new Scanner(System.in);System.out.println("请输入姓名");//控制台打印APIString 姓名=input.next();//创建工作时间输入1Scanner input1= new Scanner(System.in);System.out.println("请输入工作时间，例如：30");//控制台打印APIString 工作时间=input1.next();//创建工资输入Scanner input2= new Scanner(System.in);System.out.println("请输入工资，例如：2000000.1");//控制台打印APIString 工资=input2.next();//创建联邦所得税率输入Scanner input3= new Scanner(System.in);System.out.println("请输入联邦所得税率，例如：1.2%输入12");//控制台打印APIString 联邦所得税率=input3.next();//创建输入Scanner input4= new Scanner(System.in);System.out.println("请输入州所得税率，例如：1.2%输入12");//控制台打印APIString 州所得税率=input4.next();System.out.println("姓名:\n"+姓名+"\n工作时间:\n"+工作时间+"\n工资:\n"+工资+"\n联邦所得税率:\n"+联邦所得税率+"%"+"\n州所得税率:\n"+州所得税率+"%");//控制台打印API}}。

2011java计算机等级考试二级第二章

Java二级真题第二章1、下列变量定义中，不合法的是（）A int xB int _123C int Summer_20010_gross_salD int #dim2、下列变量名的定义中，符合java命名约定的是（）A filednameB superC IntnumD $ number3、下列符合java命名约定的是（）A package com.Bi.hrB public class xyzC int ID void setCustomerName()4、下列标识符（名字）命名规则中，正确的是（）A 类名的首字母小写B 变量和方法名的首字母大写C 接口名的首字母小写D常量名完全大写5、java中常量的保留字是（）A constB finalC finallyD native6、下列关键字中可以表示常量的是（）A finalB defaultC privateD transient7、下列数中为八进制的是（）A 27B 0×25C 026D 0288、java中的基本数据类型int在不同的操作系统平台上的字长是（）A不同的 B 32位 C 64位 D 16位9、给一个short类型变量赋值的范围是（）A -128 ~ +127B -2 147 483 648 ~ +2 147 483 647C -32 768 ~+ 32 767D -1000 ~ +100010、下列语句中错误的是（）A String[] = {"how","are"}B byte b=255C Strings="one"+"two"D int i =2+200011、下列语句中正确的是（）A System.out.pritln(1+"1");B int I = 2+'2'；C strings="on"+'one';D byte b=257;12、下列选项中为单精度数的是（）A 2B 5.2C 0.2fD 02313、下列有关java布尔类型的描述中，正确的是（）A 一种基本的数据类型，它的类型名称为booleanB 用ini表示类型C 其值可以赋给int类型的变量D 有两个值，1代表真，0代表假14、下列布尔型变量的定义中，正确且规范的是（）A BOOLEAN canceled = false;B boolean canceled=false;C boolean CANCELED=false;D boolean canceled=FALSE;15、下列关于boolean类型的叙述中，正确的是（）A 可以将boolean类型的数值转换为int类型的数值B 可以将boolean类型的数值转换为字符串集C 可以将boolean 类型的数值转换为char类型的数值D 不能将boolean类型的数值转换为其他基本数据类型16、在下列表达式中，类型可以作为int型的是（）A "abc"+"efg"B "abc"+'efg'C 'a'+'b'D 3+"4"17、public class TypeTransition {public static void main(String[] args) {char a = 'a';int i = 100;long y = 456;int aa = a + i;long yy = y - aa;System.out.println("a=" + aa);System.out.println("yy=" + yy);}}运行结果是（）A aa=197 yy=259B aa=177 yy=259C aa=543 yy=288D aa=197 yy=33318、下列属于java合法标识符的是（）A "ABC"B &5678C +rriwoD saler19、下列代表十六进制整数的是（）A 0123B 1 900C fa00D 0xa220、下列叙述中，正确的是（）A java 语言的标识符是区分大小写的B 源文件名与public类名可以不相同C 源文件扩展名jarD 源文件中public 类的数目不限21、下列属于合法标识符的是（）A _catB 5booksC +staticD -3.1415922、在java中，表示换行的转义符是（）A \nB \fC 'n'D \dd23、char类型的取值范围是（）A -27 ~ 27-1B 0 ~ 216-1C -215 ~ 215-1D 0~ 28-124、十进制数16的十六进制表示格式是（）A 0x10B 0x16C 0xa D1625、int型的public成员变量MAX_LENGTH ,该值保持为常数100，则定义这个变量的语句是（）A public int MAX_LENGTH =100B final int MAX_LENGTH =100C public const int MAX_LENGTH =100D public final int MAX_LENGTH =10026、按照java的标识符命名规范，下列表示一个类的标识符正确的是A HellowordB HelloWordC hellowordD helloWord填空题1、按照Java中的命名约定，方法名的起始字母一般都是小写，但___方法例外.2、在java中，所有数据类型的长度都是固定的，因此没有保留字___3、表达式（10*49.3）的类型是____4、java语言中的浮点数默认类型是____5、在java中，3.14159D 所表示____6、Java中的字符变量在内存中占_____位（bit）7、能打印出一个双引号的语句是System.out.println("___")8、在Java中，字符以16位的_____表示9、java中，转义符\n表示_____10、java对简单数据类型进行了类包装，int对应的包装类是____11、。

JAVA第二章课后习题答案

9.
编写程序，将十进制整数转换为二进制。 public class Tentotwo { public static void main(String[] args) { int a = 123; int remainder; int sum = 0; int k = 1; while(a != 0){ remainder = a %2; a /= 2; sum = sum + remainder * k; k *= 10; } //对目标数字求余 //对目标数字求商 //求和 //改变位数 //定义一个变量并赋给他一个十进制的值 //定义一个变量用于存储余数 //定义一个变量用于存放和 //定义一个变量控制位数
4
Hale Waihona Puke } }7.编写程序，求 100~999 之间所有的三位水仙花数。（水仙花数是指一个 n 位数 ( n≥3 )，它的每个位上的数字的 n 次幂之和等于它本身，例如：1^3 + 5^3+ 3^3 = 153） public class Shuixian { public static void main(String[] args) { int b1, b2, b3; for(int m=101; m<1000; m++) { b3=m/100; b2=m%100/10; b1=m%10; if ((b3*b3*b3+b2*b2*b2+b1*b1*b1)==m) System.out.println(m+"是一个水仙花数"); } } }
6
System.out.println("10 进制的 123 转换为 2 进制结果为：" + sum ); } }

java2实用教程试题

第1章Java 语言入门1-1开发与运行Java程序需要经过哪些主要步骤和过程？1-2怎样区分应用程序和小应用程序？应用程序的主类或小应用程序的主类必须用public修饰吗？1-3Java程序是有什么组成的？一个程序中必须要有public类吗？Java源文件的命名规则是怎样的？1-4在运行小应用程序的html文件中可以使用codebase属性制定小应用程序的字节码所驻留的目录。

如果不使用codebase属性，小应用程序的字节码文件必须和运行它的html在同一目录中，编写一个小应用程序并将它的字节码存放在某个目录中，比如c:\Boy. 把运行该小应用程序的html文件（注意其中的codebase属性）：< applet code=你的小程序的字节码wdith=20 height=30codebase=c:\boy> </applet>存放在另一个目录中（查阅有关编写网页方面的书籍，会有更详细的关于怎样在一个网页中嵌入一个小应用程序的讲解）。

第2章标识符、关键字和数据类型2-1上机运行下列程序，注意观察输出的结果。

public class E{ public static void main ( string args [ ] ){ for (int i=20302; i<=20302; i++){ System.out. println (( char ) i );}}2-2System.out. println (“你好”)；可输出字符串值，也可以使用System.out. println（）输出变量或表达式的值，只需使用并置符号：“+”将变量、表达式或一个常数值与一个字符串并置即可，如System.out. println（“”+x）；System.out. println（“：”+123+“大于”+122）等。

上机调试下列程序，注意观察结果，特别注意System.out. print（）和System.out. println（）的区别。

java程序设计课后第二章习题程序答案

public class xiti9{public static void main(String args[]) {int x=4;int y;if(x<1){y=x;}else if(x>=10){y=4*x;}else{y=3*x-2;}System.out.println("y="+y);}}习题12public class xiti12{public static void main(String args[]) {int sum=0;for(int k=1;k<=10;k++){sum=sum+k*k;}System.out.println("sum="+sum); }}习题13public class xiti13{public static void main(String args[]) {intt,a=3,b=5,c=8;if(a<b){t=a;a=b;b=t;}if(a<c){t=a;a=c;c=t;}{t=b;b=c;c=t;}System.out.println("大小顺序输出为："+a+" "+b+" "+c); }}习题14public class xiti14{public static void main(String args[]){int n=1;System.out.print("\n1-100之间的所有素数为：\n"+" 3"); for(int i=1;i<=100;i++){for(int j=2;j<=i/2;j++){if(i%j==0){break;}if(j==i/2){System.out.print(" "+i);n++;}}}System.out.println("\n共有"+n+"个素数。

java第二章练习题答案

java第二章练习题答案Java第二章练习题答案Java作为一种广泛应用的编程语言，具有着强大的功能和丰富的库。

学习Java 的过程中，练习题是巩固知识和提高编程能力的重要一环。

在第二章的练习题中，我们将探索一些基本的Java概念和语法。

下面是第二章练习题的答案，希望对大家的学习有所帮助。

1. 问题：什么是Java的标识符？标识符的命名规则是什么？答案：Java的标识符是用来标识变量、方法、类等的名称。

标识符的命名规则如下：- 必须以字母、下划线或美元符号开头；- 可以包含字母、数字、下划线或美元符号；- 大小写敏感；- 不能使用Java的关键字。

2. 问题：Java的八种基本数据类型是什么？答案：Java的八种基本数据类型分别是：- byte：字节型；- short：短整型；- int：整型；- long：长整型；- float：单精度浮点型；- double：双精度浮点型；- char：字符型；- boolean：布尔型。

3. 问题：如何声明一个整型变量并赋初值为10？答案：可以使用以下语句声明一个整型变量并赋初值为10：int num = 10;4. 问题：如何将一个字符串转换为整型？答案：可以使用Integer类的parseInt()方法将一个字符串转换为整型。

示例代码如下：String str = "123";int num = Integer.parseInt(str);5. 问题：如何声明一个常量？答案：可以使用关键字final来声明一个常量。

示例代码如下：final int MAX_NUM = 100;6. 问题：如何使用if-else语句实现条件判断？答案：可以使用if-else语句实现条件判断。

示例代码如下：int num = 10;if (num > 0) {System.out.println("num是正数");} else {System.out.println("num是负数或零");}7. 问题：如何使用for循环实现重复执行某段代码？答案：可以使用for循环实现重复执行某段代码。

java第七版课后答案——第二章

//******************************************************************** // AverageOfThree.java Author: Lewis/Loftus//// Solution to Programming Project 2.2//******************************************************************** import java.util.Scanner;public class AverageOfThree{//----------------------------------------------------------------- // Reads three integers from the user and prints their average.//----------------------------------------------------------------- public static void main <String[] args>{int num1, num2, num3;double average;Scanner scan = new Scanner <System.in>;System.out.print <"Enter the first number: ">;num1 = scan.nextInt<>;System.out.print <"Enter the second number: ">;num2 = scan.nextInt<>;System.out.print <"Enter the third number: ">;num3 = scan.nextInt<>;average = <double> <num1+num2+num3> / 3;System.out.println <"The average is: " + average>;}}//******************************************************************** // AverageOfThree2.java Author: Lewis/Loftus//// Alternate solution to Programming Project 2.2//******************************************************************** import java.util.Scanner;public class AverageOfThree2{//----------------------------------------------------------------- // Reads three integers from the user and prints their average.//----------------------------------------------------------------- public static void main <String[] args>{int num1, num2, num3;double average;Scanner scan = new Scanner <System.in>;System.out.print <"Enter three numbers: ">;num1 = scan.nextInt<>;num2 = scan.nextInt<>;num3 = scan.nextInt<>;average = <double> <num1+num2+num3> / 3;System.out.println <"The average is: " + average>;}}//******************************************************************** // Balloons.java Author: Lewis/Loftus//// Solution to Programming Project 2.17//******************************************************************** import javax.swing.JApplet;import java.awt.*;public class Balloons extends JApplet{//----------------------------------------------------------------- // Draws a set of balloons on strings.//----------------------------------------------------------------- public void paint <Graphics page>{setBackground <Color.white>;// draw the stringspage.setColor <Color.black>;page.drawLine <45, 95, 100, 300>;page.drawLine <90, 100, 100, 300>;page.drawLine <60, 100, 100, 300>;page.drawLine <122, 85, 100, 300>;page.drawLine <145, 115, 100, 300>;// draw the balloonspage.setColor <Color.blue>;page.fillOval <20, 30, 50, 65>;page.setColor <Color.yellow>;page.fillOval <70, 40, 40, 60>;page.setColor <Color.red>;page.fillOval <40, 50, 40, 55>;page.setColor <Color.green>;page.fillOval <100, 30, 45, 55>;page.setColor <Color.cyan>;page.fillOval <120, 55, 50, 60>;}}//******************************************************************** // BigDipper.java Author: Lewis/Loftus//// Solution to Programming Project 2.16//******************************************************************** import javax.swing.JApplet;import java.awt.*;public class BigDipper extends JApplet{//----------------------------------------------------------------- // Draws the Big Dipper constellation and some other stars.//----------------------------------------------------------------- public void paint <Graphics page>{setBackground <Color.black>;page.setColor <Color.white>;page.drawLine <100, 80, 110, 120>;page.drawLine <110, 120, 165, 115>;page.drawLine <165, 115, 175, 70>;page.drawLine <100, 80, 175, 70>;page.drawLine <175, 70, 245, 20>;page.drawLine <245, 20, 280, 30>;// Draw some extra starspage.fillOval <50, 50, 4, 4>;page.fillOval <70, 150, 3, 3>;page.fillOval <90, 30, 3, 3>;page.fillOval <220, 140, 4, 4>;page.fillOval <280, 170, 3, 3>;page.fillOval <310, 100, 4, 4>;page.fillOval <360, 20, 3, 3>;}}//******************************************************************** // BusinessCard.java Author: Lewis/Loftus//// Solution to Programming Project 2.20//******************************************************************** import javax.swing.JApplet;import java.awt.*;public class BusinessCard extends JApplet{//----------------------------------------------------------------- // Draws a business card.//----------------------------------------------------------------- public void paint <Graphics page>{setBackground <Color.yellow>;page.setColor <Color.red>;page.fillOval <10, 20, 60, 60>;page.setColor <Color.cyan>;page.fillRect <25, 35, 130, 25>;page.setColor <Color.black>;page.drawString <"James C. Kerplunk", 35, 50>;page.drawString <"President and CEO", 85, 80>;page.drawString <"Origin Software, Inc.", 85, 100>;page.drawLine <225, 20, 225, 80>;page.drawLine <195, 50, 255, 50>;page.setColor <Color.blue>;page.drawString <"where it all begins...", 115, 135>;}}//******************************************************************** // ChangeCounter.java Author: Lewis/Loftus//// Solution to Programming Project 2.10//******************************************************************** import java.util.Scanner;public class ChangeCounter{//----------------------------------------------------------------- // Computes the total value of a collection of coins.//----------------------------------------------------------------- public static void main <String[] args>{int quarters, dimes, nickels, pennies;int total, dollars, cents;Scanner scan = new Scanner<System.in>;System.out.print <"Enter the number of quarters: ">;quarters = scan.nextInt<>;System.out.print <"Enter the number of dimes: ">;dimes = scan.nextInt<>;System.out.print <"Enter the number of nickels: ">;nickels = scan.nextInt<>;System.out.print <"Enter the number of pennies: ">;pennies = scan.nextInt<>;total = quarters * 25 + dimes * 10 + nickels * 5 + pennies;dollars = total / 100;cents = total % 100;System.out.println <"Total value: " + dollars + " dollars and " + cents + " cents.">;}//******************************************************************** // DrawName.java Author: Lewis/Loftus//// Solution to Programming Project 2.15//******************************************************************** import javax.swing.JApplet;import java.awt.*;public class DrawName extends JApplet{//----------------------------------------------------------------- // Draws a name.//----------------------------------------------------------------- public void paint <Graphics page>{setBackground <Color.cyan>;page.setColor <Color.black>;page.drawString <"John A. Lewis", 50, 50>;}}//******************************************************************** // FloatCalculations.java Author: Lewis/Loftus//// Solution to Programming Project 2.4//******************************************************************** import java.util.Scanner;public class FloatCalculations{//----------------------------------------------------------------- // Reads two floating point numbers and prints their sum,// difference, and product.//----------------------------------------------------------------- public static void main <String[] args>{float num1, num2;Scanner scan = new Scanner <System.in>;System.out.print <"Enter the first number: ">;num1 = scan.nextFloat<>;System.out.print <"Enter the second number: ">;num2 = scan.nextFloat<>;System.out.println <"Their sum is: " + <num1+num2>>;System.out.println <"Their difference is: " + <num1-num2>>;System.out.println <"Their product is: " + <num1*num2>>;}//******************************************************************** // Fraction.java Author: Lewis/Loftus//// Solution to Programming Project 2.13//******************************************************************** import java.util.Scanner;public class Fraction{//----------------------------------------------------------------- // Computes the floating point equivalent of a fraction.//----------------------------------------------------------------- public static void main <String[] args>{int numerator, denominator;float value;Scanner scan = new Scanner<System.in>;System.out.print <"Enter the numerator: ">;numerator = scan.nextInt<>;System.out.print <"Enter the denominator: ">;denominator = scan.nextInt<>;value = <float> numerator / denominator;System.out.println <"Floating point equivalent: " + value>;}}//******************************************************************** // HousePicture.java Author: Lewis/Loftus//// Solution to Programming Project 2.19//******************************************************************** import javax.swing.JApplet;import java.awt.*;public class HousePicture extends JApplet{//----------------------------------------------------------------- // Draws a house scene.//----------------------------------------------------------------- public void paint <Graphics page>{setBackground <Color.cyan>;page.setColor <Color.gray>;page.fillRect <0, 200, 400, 50>; // groundpage.setColor <Color.blue>;page.fillRect <50, 125, 300, 100>; // housepage.setColor <Color.green>;page.fillRect <180, 175, 40, 50>; // doorpage.setColor <Color.yellow>;page.fillRect <100, 155, 40, 25>; // windowpage.fillRect <260, 155, 40, 25>; // windowpage.setColor <Color.black>;page.fillRect <40, 100, 320, 40>; // roofpage.fillOval <210, 200, 6, 6>; // doorknobpage.setColor <Color.red>;page.fillRect <80, 80, 20, 40>; // chimneypage.setColor <Color.darkGray>;page.fillOval <80, 60, 20, 20>; // smokepage.fillOval <85, 50, 15, 25>; // smokepage.fillOval <90, 45, 15, 20>; // smokepage.setColor <Color.white>;page.fillOval <200, 30, 80, 40>; // cloudpage.fillOval <230, 40, 80, 40>; // cloud}}//******************************************************************** // InfoParagraph.java Author: Lewis/Loftus//// Solution to Programming Project 2.3//******************************************************************** import java.util.Scanner;public class InfoParagraph{//----------------------------------------------------------------- // Reads information about a person and incorporates it into an// output paragraph.//----------------------------------------------------------------- public static void main <String[] args>{String name, age, college, pet;Scanner scan = new Scanner <System.in>;System.out.print <"What is your name? ">;name = scan.nextLine<>;System.out.print <"How old are you? ">;age = scan.nextLine<>;System.out.print <"What college do you attend? ">;college = scan.nextLine<>;System.out.print <"What is your pet's name? ">;pet = scan.nextLine<>;System.out.println <>;System.out.print <"Hello, my name is " + name + " and I am ">;System.out.print <age + " years\nold. I'm enjoying my time at ">; System.out.print <college + ", though\nI miss my pet " + pet>;System.out.println <" very much!">;System.out.println <>;}}//******************************************************************** // Lincoln4.java Author: Lewis/Loftus//// Solution to Programming Project 2.1//******************************************************************** public class Lincoln4{//----------------------------------------------------------------- // Prints a quote from Abraham Lincoln, including quotation// marks.//----------------------------------------------------------------- public static void main <String[] args>{System.out.println <"A quote by Abraham Lincoln:">;System.out.println <"\"Whatever you are, be a good one.\"">;}}//******************************************************************** // MilesToKilometers.java Author: Lewis/Loftus//// Solution to Programming Project 2.6//******************************************************************** import java.util.Scanner;public class MilesToKilometers{//----------------------------------------------------------------- // Converts miles into kilometers. The value for miles is read// from the user.//----------------------------------------------------------------- public static void main <String[] args>{final double MILES_PER_KILOMETER = 1.60935;double miles, kilometers;Scanner scan = new Scanner<System.in>;System.out.print <"Enter the distance in miles: ">;miles = scan.nextDouble<>;kilometers = MILES_PER_KILOMETER * miles;System.out.println <"That distance in kilometers is: " +kilometers>;}}//******************************************************************** // MoneyConversion.java Author: Lewis/Loftus//// Solution to Programming Project 2.11//******************************************************************** import java.util.Scanner;public class MoneyConversion{//----------------------------------------------------------------- // Reads a monetary amount and computes the equivalent in bills// and coins.//----------------------------------------------------------------- public static void main <String[] args>{double total;int tens, fives, ones, quarters, dimes, nickels;int remainingCents;Scanner scan = new Scanner<System.in>;System.out.print <"Enter monetary amount: ">;total = scan.nextDouble<>;remainingCents = <int> <total * 100>;tens = remainingCents / 1000;remainingCents %= 1000;fives = remainingCents / 500;remainingCents %= 500;ones = remainingCents / 100;remainingCents %= 100;quarters = remainingCents / 25;remainingCents %= 25;dimes = remainingCents / 10;remainingCents %= 10;nickels = remainingCents / 5;remainingCents %= 5;System.out.println <"That's equivalent to:">;System.out.println <tens + " ten dollar bills">;System.out.println <fives + " five dollar bills">;System.out.println <ones + " one dollar bills">;System.out.println <quarters + " quarters">;System.out.println <dimes + " dimes">;System.out.println <nickels + " nickels">;System.out.println <remainingCents + " pennies">;}}//******************************************************************** // OlympicRings.java Author: Lewis/Loftus//// Solution to Programming Project 2.18//******************************************************************** import javax.swing.JApplet;import java.awt.*;public class OlympicRings extends JApplet{//----------------------------------------------------------------- // Draws the olympic logo.//----------------------------------------------------------------- public void paint <Graphics page>{final int DIAMETER = 50;setBackground <Color.lightGray>;page.setColor <Color.blue>;page.drawOval <30, 40, DIAMETER, DIAMETER>;page.setColor <Color.yellow>;page.drawOval <60, 70, DIAMETER, DIAMETER>;page.setColor <Color.black>;page.drawOval <90, 40, DIAMETER, DIAMETER>;page.setColor <Color.green>;page.drawOval <120, 70, DIAMETER, DIAMETER>;page.setColor <Color.red>;page.drawOval <150, 40, DIAMETER, DIAMETER>;}}//******************************************************************** // PieChart.java Author: Lewis/Loftus//// Solution to Programming Project 2.22//******************************************************************** import javax.swing.JApplet;import java.awt.*;public class PieChart extends JApplet{//----------------------------------------------------------------- // Draws the pie chart with equal sections.//----------------------------------------------------------------- public void paint <Graphics page>{setBackground <Color.lightGray>;page.setColor <Color.blue>;page.fillArc <70, 25, 100, 100, 0, 45>;page.setColor <Color.yellow>;page.fillArc <70, 25, 100, 100, 45, 45>;page.setColor <Color.black>;page.fillArc <70, 25, 100, 100, 90, 45>;page.setColor <Color.green>;page.fillArc <70, 25, 100, 100, 135, 45>;page.setColor <Color.red>;page.fillArc <70, 25, 100, 100, 180, 45>;page.setColor <Color.magenta>;page.fillArc <70, 25, 100, 100, 225, 45>;page.setColor <Color.cyan>;page.fillArc <70, 25, 100, 100, 270, 45>;page.setColor <Color.orange>;page.fillArc <70, 25, 100, 100, 315, 45>;}}//******************************************************************** // Seconds.java Author: Lewis/Loftus//// Solution to Programming Project 2.8//******************************************************************** import java.util.Scanner;public class Seconds{//----------------------------------------------------------------- // Computes the total number of seconds for a given number of// hours, minutes, and seconds.//----------------------------------------------------------------- public static void main <String[] args>{final int SECONDS_PER_HOUR = 3600;final int SECONDS_PER_MINUTE = 60;int seconds, minutes, hours, totalSeconds;Scanner scan = new Scanner<System.in>;System.out.print <"Enter the number of hours: ">;hours = scan.nextInt<>;System.out.print <"Enter the number of minutes: ">;minutes = scan.nextInt<>;System.out.print <"Enter the number of seconds: ">;seconds = scan.nextInt<>;totalSeconds = hours * SECONDS_PER_HOUR +minutes * SECONDS_PER_MINUTE +seconds;System.out.println <>;System.out.println <"Total seconds: " + totalSeconds>;}}//******************************************************************** // Seconds2.java Author: Lewis/Loftus//// Solution to Programming Project 2.9//******************************************************************** import java.util.Scanner;public class Seconds2{//----------------------------------------------------------------- // Computes the number of hours, minutes, and seconds that are// equivalent to the number of seconds entered by the user.//----------------------------------------------------------------- public static void main <String[] args>{final int SECONDS_PER_HOUR = 3600;final int SECONDS_PER_MINUTE = 60;int seconds, minutes, hours;Scanner scan = new Scanner<System.in>;System.out.print <"Enter the number of seconds: ">;seconds = scan.nextInt<>;hours = seconds / SECONDS_PER_HOUR;seconds = seconds % SECONDS_PER_HOUR; // remaining secondsminutes = seconds / SECONDS_PER_MINUTE;seconds = seconds % SECONDS_PER_MINUTE; // remaining secondsSystem.out.println <>;System.out.println <"Hours: " + hours>;System.out.println <"Minutes: " + minutes>;System.out.println <"Seconds: " + seconds>;}}//******************************************************************** // ShadowName.java Author: Lewis/Loftus//// Solution to Programming Project 2.21//******************************************************************** import javax.swing.JApplet;import java.awt.*;public class ShadowName extends JApplet{//----------------------------------------------------------------- // Draws a name with a slightly offset shadow.//----------------------------------------------------------------- public void paint <Graphics page>{setBackground <Color.yellow>;page.setColor <Color.black>;page.drawString <"John A. Lewis", 50, 50>;page.setColor <Color.red>;page.drawString <"John A. Lewis", 49, 49>;}}//******************************************************************** // Snowman2.java Author: Lewis/Loftus//// Solution to Programming Project 2.14//******************************************************************** import javax.swing.JApplet;import java.awt.*;public class Snowman2 extends JApplet{//----------------------------------------------------------------- // Draws a snowman with added features.//----------------------------------------------------------------- public void paint <Graphics page>{final int MID = 130;final int TOP = 50;setBackground <Color.cyan>;page.setColor <Color.blue>;page.fillRect <0, 175, 300, 50>; // groundpage.setColor <Color.yellow>;page.fillOval <260, -40, 80, 80>; // sunpage.setColor <Color.white>;page.fillOval <MID-20, TOP, 40, 40>; // headpage.fillOval <MID-35, TOP+35, 70, 50>; // upper torsopage.fillOval <MID-50, TOP+80, 100, 60>; // lower torsopage.setColor <Color.red>;page.fillOval <MID-3, TOP+50, 6, 6>; // buttonpage.fillOval <MID-3, TOP+60, 6, 6>; // buttonpage.setColor <Color.black>;page.fillOval <MID-10, TOP+10, 5, 5>; // left eyepage.fillOval <MID+5, TOP+10, 5, 5>; // right eyepage.drawArc <MID-10, TOP+20, 20, 10, 10, 160>; // frownpage.drawLine <MID-25, TOP+60, MID-50, TOP+40>; // left armpage.drawLine <MID+25, TOP+60, MID+55, TOP+60>; // right armpage.drawLine <MID-20, TOP+5, MID+20, TOP+5>; // brim of hatpage.fillRect <MID-15, TOP-20, 30, 25>; // top of hatpage.drawString <"John Lewis", 20, 20>; // artist}}//******************************************************************** // SquareCalculations.java Author: Lewis/Loftus//// Solution to Programming Project 2.12//******************************************************************** import java.util.Scanner;public class SquareCalculations{//----------------------------------------------------------------- // Computes a square's perimeter and area given the length of// one side.//----------------------------------------------------------------- public static void main <String[] args>{int side, perimeter, area;Scanner scan = new Scanner<System.in>;System.out.print <"Enter the length of a square's side: ">;side = scan.nextInt<>;perimeter = side * 4;area = side * side;System.out.println <"Perimeter: " + perimeter>;System.out.println <"Area: " + area>;}}//******************************************************************** // TempConverter2.java Author: Lewis/Loftus//// Solution to Programming Project 2.5//******************************************************************** import java.util.Scanner;public class TempConverter2{//----------------------------------------------------------------- // Computes the Celsius equivalent of a Fahrenheit value read// from the user. Uses the formula C = <5/9><F - 32>.//----------------------------------------------------------------- public static void main <String[] args>{final int BASE = 32;final double CONVERSION_FACTOR = 5.0 / 9.0;double celsiusTemp, fahrenheitTemp;Scanner scan = new Scanner<System.in>;System.out.print <"Enter a Fahrenheit temperature: ">;fahrenheitTemp = scan.nextDouble<>;celsiusTemp = CONVERSION_FACTOR * <fahrenheitTemp - BASE>;System.out.println <"Celsius Equivalent: " + celsiusTemp>;}}//******************************************************************** // TravelTime.java Author: Lewis/Loftus//// Solution to Programming Project 2.7//******************************************************************** import java.util.Scanner;public class TravelTime{//----------------------------------------------------------------- // Converts miles into kilometers. The value for miles is read// from the user.//----------------------------------------------------------------- public static void main <String[] args>{int speed, distance;double time;Scanner scan = new Scanner<System.in>;System.out.print <"Enter the speed: ">;speed = scan.nextInt<>;System.out.print <"Enter the distance traveled: ">;distance = scan.nextInt<>;time = <double> distance / speed;System.out.println <"Time elapsed during trip: " + time>;}}。

java习题及答案第2章习题参考答案

第2章习题解答1. 安装JDK开发运行环境：从官方网站下载最新版的JDK安装软件，安装JDK软件。

答：JDK开发运行环境的安装大致有三步,一是下载JDK安装软件,二是安装JDK软件,三是确认JDK是否正确安装。

建议从官方网站下载JDK软件。

详细安装过程略。

2. 安装集成开发环境Eclipse：从官方网站下载最新版的Eclipse软件，将其解压缩到适当的文件夹中，运行Eclipse并配置其所需要的Java运行环境，创建workspace文件夹，创建一个Java Application项目并编写简单的Java程序，执行该程序验证安装过程的正确性。

答：安装集成开发环境Eclipse 大致有三步，一是下载Eclipse软件（有多种版本可供选择，根据实际情况或需要下载必要的版本），二是安装Eclipse软件（通常只需要将压缩软件解压后放在适当的文件夹下即可），三是创建workspace文件夹用于存放Java程序。

建议从官方网站下载Eclipse软件。

详细安装过程略。

3. 从网络上查找一个感兴趣的Java应用程序，在Eclipse开发环境中编辑调试运行该程序。

答：有关过程略。

4. 简述建立Java有关软件开发运行环境的主要步骤。

答：建立Java有关软件开发运行的主要步骤有：一是下载安装JDK；二是下载安装Eclipse 或netbeansws等这样的集成开发环境；三是运行集成开发环境，建立Java项目，编写Java 程序，调试运行。

最后，还需要考虑开发好的程序的部署和运行。

5. 从官方网站下载《The Java™ Language Specification》（Java SE 7 Edition），并打开阅读该文档。

答：在线问答的网址是://docs.oracle/javase/specs/jls/se7/html/ 。

下载PDF文档的网址是ht3tp://docs.oracle/javase/specs/。

java第二章代码练习.doc

运行结果截图:
//:NumberalExpression.java package com.chenlong; public class NumberalExpression { public static void main(String[] args) { int decimal = 65; int octal = 0101; int hexadecimal = 0x41; System.out.println("SA进 " + decimal); System.out.println("Qk进 0101对应进 " + octal); System.out.println("SAQm进 0x41对应进 " + hexadecimal); } }
运行结果截图:
//:primitiveWidening.java package com.chenlong; public class primitiveWidening { public static void main(String[] args) { char c = '\u0041'; System.out.println("char ->long:c=\'\\u0041\''->"); long l =c; System.out.println("l=0x"+Long.toHexString (l)); float f = 1.23f; double d =f; System.out.println("float->double:f = 1.23f->d=" + d); int big =1234567890; float approx =big; System.out.println("int->float:(1234567890-(int)1234567890f)v„结果:"+ (big -(int)approx)); long large =1234567890123456789L; double pricisionLosing =large; System.out.println("long->double:(1234567890123456789L-(long)1234567890123456789D) v„结果:" +(large-(long)pricisionLosing)); } } 第 7 页，共 19 页

jAVA2程序设计基础第二章精品PPT课件

Java中整型常量可以分为十进制、十六进制和八进制。而整型变量的定义可分为四种：byte型、short型、int型和long型。 4. 浮点类型
浮点类型可分为 float(32位)和double(64位)两种类型。float 型叫做单精度浮点数。
返回
2.1.4 Java中的命名规则
一般来说，变量命名只要按照标识符的命名规则来命名即可，但为了程序更加规范和易读，在Java语言规范中有以下命名规则：
返回
2.1.3 Java语言中的基本数据类型
1. 逻辑类型逻辑类型又称布尔类型，其值只有两种：真(true)和假(false)。它使用
关键字boolean 来定义逻辑变量。 2. 字符类型
Java中每一个字符占两个字节，它使用的是unicode字符集，因此可使用的常量共有65535个。它使用关键字char来定义字符变量。 3. 整数类型
第2章 Java编程基础
教学提示：在上一章中，我们对Java语言的历史、原理、开发环境的搭建和系统环境变量的设置进行了介绍，使读者对其有一个基本的了解。但仅仅掌握这些还不够。本章将进一步介绍Java语言程序设计的方法与技巧，任何技巧和能力的形成都是以基础知识作为铺垫的，因此本章把注意力集中在Java语言最基础的知识方面，这涉及到数据类型以及定义在其上的运算、表达式、基本语法格式、变量及变量的作用域和运算符等。学习这些内容后，读者对Java语言会有一个更深的了解。
返回
2.1.5 Java中的一些注意事项
(1) Java是要区分大小写的。 (2) 功能执行语句的后面必须以分号(;)结束，这是提示该执行语句结束的标志，而且这个分号是英文的(;)而不能是中文的(；)。
返回
2.2 变量及变量的作用域

java第七版课后答案——第二章

//******************************************************************** // AverageOfThree.java Author: Lewis/Loftus//// Solution to Programming Project 2.2//******************************************************************** import java.util.Scanner;public class AverageOfThree{//----------------------------------------------------------------- // Reads three integers from the user and prints their average.//----------------------------------------------------------------- public static void main (String[] args){int num1, num2, num3;double average;Scanner scan = new Scanner (System.in);System.out.print ("Enter the first number: ");num1 = scan.nextInt();System.out.print ("Enter the second number: ");num2 = scan.nextInt();System.out.print ("Enter the third number: ");num3 = scan.nextInt();average = (double) (num1+num2+num3) / 3;System.out.println ("The average is: " + average);}}//******************************************************************** // AverageOfThree2.java Author: Lewis/Loftus//// Alternate solution to Programming Project 2.2//******************************************************************** import java.util.Scanner;public class AverageOfThree2{//----------------------------------------------------------------- // Reads three integers from the user and prints their average.//----------------------------------------------------------------- public static void main (String[] args){int num1, num2, num3;double average;Scanner scan = new Scanner (System.in);System.out.print ("Enter three numbers: ");num1 = scan.nextInt();num2 = scan.nextInt();num3 = scan.nextInt();average = (double) (num1+num2+num3) / 3;System.out.println ("The average is: " + average);}}//******************************************************************** // Balloons.java Author: Lewis/Loftus//// Solution to Programming Project 2.17//********************************************************************import javax.swing.JApplet;import java.awt.*;public class Balloons extends JApplet{//----------------------------------------------------------------- // Draws a set of balloons on strings.//----------------------------------------------------------------- public void paint (Graphics page){setBackground (Color.white);// draw the stringspage.setColor (Color.black);page.drawLine (45, 95, 100, 300);page.drawLine (90, 100, 100, 300);page.drawLine (60, 100, 100, 300);page.drawLine (122, 85, 100, 300);page.drawLine (145, 115, 100, 300);// draw the balloonspage.setColor (Color.blue);page.fillOval (20, 30, 50, 65);page.setColor (Color.yellow);page.fillOval (70, 40, 40, 60);page.setColor (Color.red);page.fillOval (40, 50, 40, 55);page.setColor (Color.green);page.fillOval (100, 30, 45, 55);page.setColor (Color.cyan);page.fillOval (120, 55, 50, 60);}}//******************************************************************** // BigDipper.java Author: Lewis/Loftus//// Solution to Programming Project 2.16//********************************************************************import javax.swing.JApplet;import java.awt.*;public class BigDipper extends JApplet{//----------------------------------------------------------------- // Draws the Big Dipper constellation and some other stars.//----------------------------------------------------------------- public void paint (Graphics page){setBackground (Color.black);page.setColor (Color.white);page.drawLine (100, 80, 110, 120);page.drawLine (110, 120, 165, 115);page.drawLine (165, 115, 175, 70);page.drawLine (100, 80, 175, 70);page.drawLine (175, 70, 245, 20);page.drawLine (245, 20, 280, 30);// Draw some extra starspage.fillOval (50, 50, 4, 4);page.fillOval (70, 150, 3, 3);page.fillOval (90, 30, 3, 3);page.fillOval (220, 140, 4, 4);page.fillOval (280, 170, 3, 3);page.fillOval (310, 100, 4, 4);page.fillOval (360, 20, 3, 3);}}//******************************************************************** // BusinessCard.java Author: Lewis/Loftus//// Solution to Programming Project 2.20//********************************************************************import javax.swing.JApplet;import java.awt.*;public class BusinessCard extends JApplet{//----------------------------------------------------------------- // Draws a business card.//----------------------------------------------------------------- public void paint (Graphics page){setBackground (Color.yellow);page.setColor (Color.red);page.fillOval (10, 20, 60, 60);page.setColor (Color.cyan);page.fillRect (25, 35, 130, 25);page.setColor (Color.black);page.drawString ("James C. Kerplunk", 35, 50);page.drawString ("President and CEO", 85, 80);page.drawString ("Origin Software, Inc.", 85, 100);page.drawLine (225, 20, 225, 80);page.drawLine (195, 50, 255, 50);page.setColor (Color.blue);page.drawString ("where it all begins...", 115, 135);}}//******************************************************************** // ChangeCounter.java Author: Lewis/Loftus//// Solution to Programming Project 2.10//******************************************************************** import java.util.Scanner;public class ChangeCounter{//----------------------------------------------------------------- // Computes the total value of a collection of coins.//----------------------------------------------------------------- public static void main (String[] args){int quarters, dimes, nickels, pennies;int total, dollars, cents;Scanner scan = new Scanner(System.in);System.out.print ("Enter the number of quarters: ");quarters = scan.nextInt();System.out.print ("Enter the number of dimes: ");dimes = scan.nextInt();System.out.print ("Enter the number of nickels: ");nickels = scan.nextInt();System.out.print ("Enter the number of pennies: ");pennies = scan.nextInt();total = quarters * 25 + dimes * 10 + nickels * 5 + pennies;dollars = total / 100;cents = total % 100;System.out.println ("Total value: " + dollars + " dollars and " + cents + " cents.");}}//******************************************************************** // DrawName.java Author: Lewis/Loftus//// Solution to Programming Project 2.15//********************************************************************import javax.swing.JApplet;import java.awt.*;public class DrawName extends JApplet{//----------------------------------------------------------------- // Draws a name.//----------------------------------------------------------------- public void paint (Graphics page){setBackground (Color.cyan);page.setColor (Color.black);page.drawString ("John A. Lewis", 50, 50);}}//******************************************************************** // FloatCalculations.java Author: Lewis/Loftus//// Solution to Programming Project 2.4//******************************************************************** import java.util.Scanner;public class FloatCalculations{//----------------------------------------------------------------- // Reads two floating point numbers and prints their sum,// difference, and product.//----------------------------------------------------------------- public static void main (String[] args){float num1, num2;Scanner scan = new Scanner (System.in);System.out.print ("Enter the first number: ");num1 = scan.nextFloat();System.out.print ("Enter the second number: ");num2 = scan.nextFloat();System.out.println ("Their sum is: " + (num1+num2));System.out.println ("Their difference is: " + (num1-num2));System.out.println ("Their product is: " + (num1*num2));}}//******************************************************************** // Fraction.java Author: Lewis/Loftus//// Solution to Programming Project 2.13//******************************************************************** import java.util.Scanner;public class Fraction{//----------------------------------------------------------------- // Computes the floating point equivalent of a fraction.//----------------------------------------------------------------- public static void main (String[] args){int numerator, denominator;float value;Scanner scan = new Scanner(System.in);System.out.print ("Enter the numerator: ");numerator = scan.nextInt();System.out.print ("Enter the denominator: ");denominator = scan.nextInt();value = (float) numerator / denominator;System.out.println ("Floating point equivalent: " + value);}}//******************************************************************** // HousePicture.java Author: Lewis/Loftus//// Solution to Programming Project 2.19//********************************************************************import javax.swing.JApplet;import java.awt.*;public class HousePicture extends JApplet{//----------------------------------------------------------------- // Draws a house scene.//----------------------------------------------------------------- public void paint (Graphics page){setBackground (Color.cyan);page.setColor (Color.gray);page.fillRect (0, 200, 400, 50); // groundpage.setColor (Color.blue);page.fillRect (50, 125, 300, 100); // housepage.setColor (Color.green);page.fillRect (180, 175, 40, 50); // doorpage.setColor (Color.yellow);page.fillRect (100, 155, 40, 25); // windowpage.fillRect (260, 155, 40, 25); // windowpage.setColor (Color.black);page.fillRect (40, 100, 320, 40); // roofpage.fillOval (210, 200, 6, 6); // doorknobpage.setColor (Color.red);page.fillRect (80, 80, 20, 40); // chimneypage.setColor (Color.darkGray);page.fillOval (80, 60, 20, 20); // smokepage.fillOval (85, 50, 15, 25); // smokepage.fillOval (90, 45, 15, 20); // smokepage.setColor (Color.white);page.fillOval (200, 30, 80, 40); // cloudpage.fillOval (230, 40, 80, 40); // cloud}}//******************************************************************** // InfoParagraph.java Author: Lewis/Loftus//// Solution to Programming Project 2.3//********************************************************************import java.util.Scanner;public class InfoParagraph{//----------------------------------------------------------------- // Reads information about a person and incorporates it into an// output paragraph.//----------------------------------------------------------------- public static void main (String[] args){String name, age, college, pet;Scanner scan = new Scanner (System.in);System.out.print ("What is your name? ");name = scan.nextLine();System.out.print ("How old are you? ");age = scan.nextLine();System.out.print ("What college do you attend? ");college = scan.nextLine();System.out.print ("What is your pet's name? ");pet = scan.nextLine();System.out.println ();System.out.print ("Hello, my name is " + name + " and I am ");System.out.print (age + " years\nold. I'm enjoying my time at "); System.out.print (college + ", though\nI miss my pet " + pet);System.out.println (" very much!");System.out.println ();}}//******************************************************************** // Lincoln4.java Author: Lewis/Loftus//// Solution to Programming Project 2.1//********************************************************************public class Lincoln4{//----------------------------------------------------------------- // Prints a quote from Abraham Lincoln, including quotation// marks.//----------------------------------------------------------------- public static void main (String[] args){System.out.println ("A quote by Abraham Lincoln:");System.out.println ("\"Whatever you are, be a good one.\"");}}//******************************************************************** // MilesToKilometers.java Author: Lewis/Loftus//// Solution to Programming Project 2.6//******************************************************************** import java.util.Scanner;public class MilesToKilometers{//----------------------------------------------------------------- // Converts miles into kilometers. The value for miles is read// from the user.//----------------------------------------------------------------- public static void main (String[] args){final double MILES_PER_KILOMETER = 1.60935;double miles, kilometers;Scanner scan = new Scanner(System.in);System.out.print ("Enter the distance in miles: ");miles = scan.nextDouble();kilometers = MILES_PER_KILOMETER * miles;System.out.println ("That distance in kilometers is: " +kilometers);}}//******************************************************************** // MoneyConversion.java Author: Lewis/Loftus//// Solution to Programming Project 2.11//******************************************************************** import java.util.Scanner;public class MoneyConversion{//----------------------------------------------------------------- // Reads a monetary amount and computes the equivalent in bills// and coins.//----------------------------------------------------------------- public static void main (String[] args){double total;int tens, fives, ones, quarters, dimes, nickels;int remainingCents;Scanner scan = new Scanner(System.in);System.out.print ("Enter monetary amount: ");total = scan.nextDouble();remainingCents = (int) (total * 100);tens = remainingCents / 1000;remainingCents %= 1000;fives = remainingCents / 500;remainingCents %= 500;ones = remainingCents / 100;remainingCents %= 100;quarters = remainingCents / 25;remainingCents %= 25;dimes = remainingCents / 10;remainingCents %= 10;nickels = remainingCents / 5;remainingCents %= 5;System.out.println ("That's equivalent to:");System.out.println (tens + " ten dollar bills");System.out.println (fives + " five dollar bills");System.out.println (ones + " one dollar bills");System.out.println (quarters + " quarters");System.out.println (dimes + " dimes");System.out.println (nickels + " nickels");System.out.println (remainingCents + " pennies");}}//******************************************************************** // OlympicRings.java Author: Lewis/Loftus//// Solution to Programming Project 2.18//********************************************************************import javax.swing.JApplet;import java.awt.*;public class OlympicRings extends JApplet{//----------------------------------------------------------------- // Draws the olympic logo.//----------------------------------------------------------------- public void paint (Graphics page){final int DIAMETER = 50;setBackground (Color.lightGray);page.setColor (Color.blue);page.drawOval (30, 40, DIAMETER, DIAMETER);page.setColor (Color.yellow);page.drawOval (60, 70, DIAMETER, DIAMETER);page.setColor (Color.black);page.drawOval (90, 40, DIAMETER, DIAMETER);page.setColor (Color.green);page.drawOval (120, 70, DIAMETER, DIAMETER);page.setColor (Color.red);page.drawOval (150, 40, DIAMETER, DIAMETER);}}//******************************************************************** // PieChart.java Author: Lewis/Loftus//// Solution to Programming Project 2.22//******************************************************************** import javax.swing.JApplet;import java.awt.*;public class PieChart extends JApplet{//----------------------------------------------------------------- // Draws the pie chart with equal sections.//----------------------------------------------------------------- public void paint (Graphics page){setBackground (Color.lightGray);page.setColor (Color.blue);page.fillArc (70, 25, 100, 100, 0, 45);page.setColor (Color.yellow);page.fillArc (70, 25, 100, 100, 45, 45);page.setColor (Color.black);page.fillArc (70, 25, 100, 100, 90, 45);page.setColor (Color.green);page.fillArc (70, 25, 100, 100, 135, 45);page.setColor (Color.red);page.fillArc (70, 25, 100, 100, 180, 45);page.setColor (Color.magenta);page.fillArc (70, 25, 100, 100, 225, 45);page.setColor (Color.cyan);page.fillArc (70, 25, 100, 100, 270, 45);page.setColor (Color.orange);page.fillArc (70, 25, 100, 100, 315, 45);}}//******************************************************************** // Seconds.java Author: Lewis/Loftus//// Solution to Programming Project 2.8//******************************************************************** import java.util.Scanner;public class Seconds{//----------------------------------------------------------------- // Computes the total number of seconds for a given number of// hours, minutes, and seconds.//-----------------------------------------------------------------public static void main (String[] args){final int SECONDS_PER_HOUR = 3600;final int SECONDS_PER_MINUTE = 60;int seconds, minutes, hours, totalSeconds;Scanner scan = new Scanner(System.in);System.out.print ("Enter the number of hours: ");hours = scan.nextInt();System.out.print ("Enter the number of minutes: ");minutes = scan.nextInt();System.out.print ("Enter the number of seconds: ");seconds = scan.nextInt();totalSeconds = hours * SECONDS_PER_HOUR +minutes * SECONDS_PER_MINUTE +seconds;System.out.println ();System.out.println ("Total seconds: " + totalSeconds);}}//******************************************************************** // Seconds2.java Author: Lewis/Loftus//// Solution to Programming Project 2.9//******************************************************************** import java.util.Scanner;public class Seconds2{//----------------------------------------------------------------- // Computes the number of hours, minutes, and seconds that are// equivalent to the number of seconds entered by the user.//----------------------------------------------------------------- public static void main (String[] args){final int SECONDS_PER_HOUR = 3600;final int SECONDS_PER_MINUTE = 60;int seconds, minutes, hours;Scanner scan = new Scanner(System.in);System.out.print ("Enter the number of seconds: ");seconds = scan.nextInt();hours = seconds / SECONDS_PER_HOUR;seconds = seconds % SECONDS_PER_HOUR; // remaining secondsminutes = seconds / SECONDS_PER_MINUTE;seconds = seconds % SECONDS_PER_MINUTE; // remaining secondsSystem.out.println ();System.out.println ("Hours: " + hours);System.out.println ("Minutes: " + minutes);System.out.println ("Seconds: " + seconds);}}//******************************************************************** // ShadowName.java Author: Lewis/Loftus//// Solution to Programming Project 2.21//********************************************************************import javax.swing.JApplet;import java.awt.*;public class ShadowName extends JApplet{//----------------------------------------------------------------- // Draws a name with a slightly offset shadow.//----------------------------------------------------------------- public void paint (Graphics page){setBackground (Color.yellow);page.setColor (Color.black);page.drawString ("John A. Lewis", 50, 50);page.setColor (Color.red);page.drawString ("John A. Lewis", 49, 49);}}//******************************************************************** // Snowman2.java Author: Lewis/Loftus//// Solution to Programming Project 2.14//********************************************************************import javax.swing.JApplet;import java.awt.*;public class Snowman2 extends JApplet{//----------------------------------------------------------------- // Draws a snowman with added features.//----------------------------------------------------------------- public void paint (Graphics page){final int MID = 130;final int TOP = 50;setBackground (Color.cyan);page.setColor (Color.blue);page.fillRect (0, 175, 300, 50); // groundpage.setColor (Color.yellow);page.fillOval (260, -40, 80, 80); // sunpage.setColor (Color.white);page.fillOval (MID-20, TOP, 40, 40); // headpage.fillOval (MID-35, TOP+35, 70, 50); // upper torsopage.fillOval (MID-50, TOP+80, 100, 60); // lower torsopage.setColor (Color.red);page.fillOval (MID-3, TOP+50, 6, 6); // buttonpage.fillOval (MID-3, TOP+60, 6, 6); // buttonpage.setColor (Color.black);page.fillOval (MID-10, TOP+10, 5, 5); // left eyepage.fillOval (MID+5, TOP+10, 5, 5); // right eyepage.drawArc (MID-10, TOP+20, 20, 10, 10, 160); // frownpage.drawLine (MID-25, TOP+60, MID-50, TOP+40); // left armpage.drawLine (MID+25, TOP+60, MID+55, TOP+60); // right armpage.drawLine (MID-20, TOP+5, MID+20, TOP+5); // brim of hatpage.fillRect (MID-15, TOP-20, 30, 25); // top of hatpage.drawString ("John Lewis", 20, 20); // artist}}//******************************************************************** // SquareCalculations.java Author: Lewis/Loftus//// Solution to Programming Project 2.12//******************************************************************** import java.util.Scanner;public class SquareCalculations{//----------------------------------------------------------------- // Computes a square's perimeter and area given the length of// one side.//----------------------------------------------------------------- public static void main (String[] args){int side, perimeter, area;Scanner scan = new Scanner(System.in);System.out.print ("Enter the length of a square's side: ");side = scan.nextInt();perimeter = side * 4;area = side * side;System.out.println ("Perimeter: " + perimeter);System.out.println ("Area: " + area);}}//********************************************************************// TempConverter2.java Author: Lewis/Loftus//// Solution to Programming Project 2.5//******************************************************************** import java.util.Scanner;public class TempConverter2{//----------------------------------------------------------------- // Computes the Celsius equivalent of a Fahrenheit value read// from the user. Uses the formula C = (5/9)(F - 32).//----------------------------------------------------------------- public static void main (String[] args){final int BASE = 32;final double CONVERSION_FACTOR = 5.0 / 9.0;double celsiusTemp, fahrenheitTemp;Scanner scan = new Scanner(System.in);System.out.print ("Enter a Fahrenheit temperature: ");fahrenheitTemp = scan.nextDouble();celsiusTemp = CONVERSION_FACTOR * (fahrenheitTemp - BASE);System.out.println ("Celsius Equivalent: " + celsiusTemp);}}//******************************************************************** // TravelTime.java Author: Lewis/Loftus//// Solution to Programming Project 2.7//******************************************************************** import java.util.Scanner;public class TravelTime{//----------------------------------------------------------------- // Converts miles into kilometers. The value for miles is read// from the user.//-----------------------------------------------------------------public static void main (String[] args){int speed, distance;double time;Scanner scan = new Scanner(System.in);System.out.print ("Enter the speed: ");speed = scan.nextInt();System.out.print ("Enter the distance traveled: ");distance = scan.nextInt();time = (double) distance / speed;System.out.println ("Time elapsed during trip: " + time); }}。

JAVA编程思想第二章习题答案

JAVA编程思想第⼆章习题答案// access/AccessTest.java// TIJ4 Chapter Access, Exercise 5, page 227/* Create a class with public, private, protected and package-access fields and * method members. Create an object of this class and see what kind of compiler * messages you get when you try to access all the class members. Be aware that * classes in the same directory are part of the "default" package.*//* in same directory:* package access;** public class FourWays {* int a = 0;* public int b = 1;* protected int c = 2;* private int d = 3;* FourWays() { System.out.println("FourWays() constructor"); }* void showa() { System.out.println(a); }* public void showb() { System.out.println(b); }* protected void showc() { System.out.println(c); }* private void showd() { System.out.println(d); }* }*/package access; // run command java access.AccessTestpublic class AccessTest {public static void main(String[] args) {FourWays fw = new FourWays();fw.showa();fw.showb();fw.showc();fw.a = 10;fw.b = 20;fw.c = 30;fw.showa();fw.showb();fw.showc();//! fw.showd(); // private access, compiler can't touch}}// access/Collision.java// TIJ4 Chapter Access, Exercise 2, page 217/* Take the code fragments in this section and turn them into a program and* verify that collisions do occur.*/import net.mindview.simple.*;import java.util.*;public class Collision {public static void main(String[] args) {// Vector v = new Vector(); // ambiquous collisionnet.mindview.simple.Vector v1 = new net.mindview.simple.Vector();java.util.Vector v2 = new java.util.Vector();}}// access/ConnectionManager.java// TIJ4 Chapter Access, Exercise 8, page 233/* Following the form of the example Lunch.java, create a class called* ConnectionManager that manages a fixed array of Connection objects. The client* programmer must not be able to explicitly create Connection objects, but can* only get them via a static method in ConnectionManager. When ConnectionManager * runs out of objects, it returns a null reference. Test the classes in main(). */ package access;class Connection {private static int count = 0;private int i = 0;private Connection() { System.out.println("Connection()");}// Allow creation via static method:static Connection makeConnection() {count++;return new Connection();}public static int howMany() { return count; }public String toString() {return ("Connection " + count);}}public class ConnectionManager {static int howManyLeft = 3;static Connection[] ca = new Connection[3];{for(Connection x : ca)x = Connection.makeConnection();}public static Connection getConnection() {if(howManyLeft > 0)return ca[--howManyLeft];else {System.out.println("No more connections");return null;}}public static void main(String[] args) {ConnectionManager cm = new ConnectionManager();System.out.println(cm.howManyLeft);cm.getConnection();System.out.println(howManyLeft);cm.getConnection();System.out.println(howManyLeft);cm.getConnection();System.out.println(cm.getConnection());System.out.println(howManyLeft);}}// access/cookie2/CookieMonster.java// TIJ4 Chapter Access, Exercise 4, page 227// Show that protected methods have package access but are not public. /* In directory Cookie2:* //access/cookie2/Cookie.java* //Creates a library* package access.cookie2;** public class Cookie {* public Cookie() {* System.out.println("Cookie contstructor");* }* protected void bite() { System.out.println("bite"); }* }*/package access.cookie2;public class CookieMonster {public static void main(String[] args) {Cookie x = new Cookie();x.bite(); // package access to protected method}}// access/CookieThief.java// TIJ4 Chapter Access, Exercise 4, page 227// Show that protected methods have package access but are not public. /* In directory Cookie2:* //access/cookie2/Cookie.java* //Creates a library* package access.cookie2;** public class Cookie {* public Cookie() {* System.out.println("Cookie contstructor");* }* protected void bite() { System.out.println("bite"); }* }*/import access.cookie2.*;public class CookieThief {public static void main(String[] args) {Cookie x = new Cookie();//! x.bite(); // access protected}}// access/debug/Debug.java// TIJ4 Chapter Access, Exercise 3, page 220/* Create two packages: debug and debugoff, containing an identical class with a * debug() method. The first version displays its String argument to the console, * the second does nothing. Use a static import line to import the class into a test * program, and demonstrate the conditional compilation effect.*//* In directory access/debugoff:* // access/debugoff/Debug.java* package access.debugoff;** public class Debug {* public static void debug(String s) { }* }*/package access.debug;public class Debug {public static void debug(String s) {System.out.println(s);}// TIJ4 chapter Access, Exercise 9, page 233/* Create in access/local directory in your CLASSPATH:* // access/local/PackagedClass.java* package access.local;** class PackagedClass {* public PackagedClass() {* System.out.println("Creating a packaged class");* }* }* // Then, in another directrory create the file below and explain why compiler* generates error. Would making Foreign class part of access.local change anything? */// access/foreign/Foreign.javapackage access.foreign;import access.local.*;public class Foreign {public static void main(String[] args) {PackagedClass pc = new PackagedClass();}}/* Compiler error because: PackagedClass in not public, so no access outside of* package. Moving Foreign to local would allow package access to PackagedClass. */// MakeWidget.java// TIJ4 Chapter Access, Exercise 7, page 230/* Create the library according to the code fragments describing access and Widget. * Create a Widget in a class that is not part of the access package.*//* in access package:* // access/Widget.java* package access;** public class Widget {* public Widget() { System.out.println("Widget()"); }* }*/import access.*;public class MakeWidget {public static void main(String[] args) {Widget w = new Widget();}}// access/ProtectedData.java// TIJ4 Chapter Access, Exercise 6, page 228/* Create a class with protected data. Create a second class in the same file with* a method that manipulates the protected data in the first class.*/class SomeData {protected int a = 13;}class DataChanger {static void change(SomeData sd, int i) { sd.a = i; }}public class ProtectedData {public static void main(String[] args) {SomeData x = new SomeData();System.out.println(x.a);DataChanger.change(x, 99);System.out.println(x.a);}}// access/UnpackagedMyClass.java// TIJ4 Chapter Access, Exercise 1, page 217// Create a class in a package. Create an instance of your class outside of that package. /* In another directory:* // access/mypackage/MyPackagedClass.java** package access.mypackage;** public class MyPackagedClass {* public MyPackagedClass() {System.out.println("MyPackagedClass()");}* }*/public class UnpackagedMyClass {public static void main(String[] args) {access.mypackage.MyPackagedClass m = new access.mypackage.MyPackagedClass(); }。

考试酷java 第二章

Java入门经典第2章动手写Hello World知识点练习答案及课后习题答案

java语言程序设计第二章编程练习题（1-11）

2011java计算机等级考试二级第二章

JAVA第二章 课后习题答案

java2实用教程试题

java程序设计课后第二章习题程序答案

java第二章练习题答案

java第七版课后答案——第二章

java习题及答案第2章 习题参考答案

java第二章代码练习.doc

jAVA2程序设计基础第二章精品PPT课件

java第七版课后答案——第二章

JAVA编程思想第二章习题答案

JAVA第二章课后习题答案

java习题及答案第2章习题参考答案