阿里巴巴(中国)网络技术有限公司JAVA面试题

选择题部分1:1.What will happen when you attempt to compile and run the following code?2.3.class Base4.5.{6.7.int i=99;8.9.public void amethod()10.11.{12.13.System.out.println("Base.amethod()");14.15.}16.17.Base()18.19.{20.21.amethod();22.23.}24.25.}26.27.public class Derived extends Base28.29.{30.31.int i=-1;32.33.34.35.public static void main(String argv[])36.37.{38.39.Base b=new Derived();40.41.System.out.println(b.i);43. b.amethod();44.45.}46.47.public void amethod()48.49.{50.51.System.out.println("Derived.amethod()");52.53.}54.55.}56.57.Choices:A.Derived.amethod()-1Derived.amethod()B.Derived.amethod()99Derived.amethod()pile time errorD.Derived.amethod()2:1.Which is the most appropriate code snippet that can be inserted at line18in the following code?2.3.(Assume that the code is compiled and run with assertions enabled)4.5.1.import java.util.*;6.7.2.8.9.3.public class AssertTest10.11.4.{12.13.5.private HashMap cctld;14.15.6.16.17.7.public AssertTest()19.8.{20.tld=new HashMap();22.tld.put("in","India");24.tld.put("uk","United Kingdom");26.tld.put("au","Australia");28.29.13.//more code...30.31.14.}32.33.15.//other methods....34.35.16.public String getCountry(String countryCode)36.37.17.{38.39.18.//What should be inserted here?40.41.19.String country=(String)cctld.get(countryCode);42.43.20.return country;44.45.21.}46.47.22.}A.assert countryCode!=null;B.assert countryCode!=null:"Country code can not be null";C.assert cctld!=null:"No country code data is available";D.assert cctld:"No country code data is available";3:1.What will be the result of executing the following code?2.boolean a=true;3.boolean b=false;4.boolean c=true;5.if(a==true)6.if(b==true)7.if(c==true)System.out.println("Some things are true in this world");8.else System.out.println("Nothing is true in this world!");9.else if(a&&(b=c))System.out.println("It's too confusing to tell what is true and what is false");10.else System.out.println("Hey this won't compile");11.12.Choices:A.The code won't compileB."Some things are true in this world"will be printedC."Hey this won't compile"will be printedD.None of these4:A class design requires that a member variable should be accessible only by same package, which modifer word should be used?A.protectedB.publicC.no modiferD.private5:Which is the main()method return of a application?A.StringB.byteC.charD.void6:在软件生命周期中，下列哪个说法是不准确的?A.软件生命周期分为计划、开发和运行三个阶段B.在计划阶段要进行问题焉醛和需求分析C.在开发后期要进行编写代码和软件测试D.在运行阶段主要是进行软件维护7:1.Given the following class definition:2.class A{3.protected int i;4.A(int i){5.this.i=i;6.}7.}8.which of the following would be a valid inner class for this class?9.Select valid answer:A.class B{}B.class B extends A{}C.class B extends A{B(){System.out.println(“i=”+i);}}D.class B{class A{}}8:1.String s=”Example String”;Which operation is not legal?A.int i=s.length();B.s[3]=”x”;C.String short_s=s.trim();D.String t=”root”+s;9:Which fragments are not correct in Java source file?A.package testpackage;public class Test{//do something...}B.import java.io.*;package testpackage;public class Test{//do something...}C.import java.io.*;class Person{//do something...}public class Test{//do something...}D.import java.io.*;import java.awt.*;public class Test{//do something...}10:Which of the following statements are true?A.The automatic garbage collection of the JVM prevents programs from ever running outof memoryB.A program can suggest that garbage collection be performed and force itC.Garbage collection is platform independentD.An object becomes eligible for garbage collection when all references denoting it areset to null.11:1.What results from attempting to compile and run the following code?2.3.public class Ternary4.5.{6.7.public static void main(String args[])8.9.{10.11.int a=5;12.13.System.out.println("Value is-"+((a<5)?9.9:9));14.15.}16.17.}18.19.Choices:A.prints:Value is-9pilation errorC.prints:Value is-5D.None of these12:1.Give the following java source fragement:2.//point x3.public class Interesting{4.//do something5.}6.Which statement is correctly Java syntax at point x?A.public class MyClass{//do other thing…}B.static int PI=3.14C.class MyClass{//do something…}D.none13:1.What will happen when you attempt to compile and run the following code?2.3.(Assume that the code is compiled and run with assertions enabled.)4.5.public class AssertTest{6.7.public void methodA(int i){8.9.assert i>=0:methodB();10.11.System.out.println(i);12.13.}14.15.public void methodB(){16.17.System.out.println("The value must not be negative");18.19.}20.21.public static void main(String args[]){22.23.AssertTest test=new AssertTest();24.25.test.methodA(-10);26.27.}28.29.}A.it will print-10B.it will result in AssertionError showing the message-“the value must not be negative”.C.the code will not compile.D.None of these.14:1.Give the code fragment:2.if(x>4){3.System.out.println(“Test1”);}4.else if(x>9){5.System.out.println(“Test2”);}6.else{7.System.out.println(“Test3”);}8.Which range of value x would produce of output“Test2”?A.x<4B.x>4C.x>9D.None简答题15:将某个文件从一个目录拷贝到另一个目录下（不能用C/C++中的函数或类）。