阿里巴巴(中国)网络技术有限公司 面试 笔试

选择题

1: 1. What will happen when you attempt to compile and run the following code?

2.

3. class Base

4.

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 Base

28.

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() -1 Derived.amethod()

B.Derived.amethod() 99

pile time error

D.Derived.amethod()

2: 1. Which is the most appropriate code snippet that can be inserted at line 18 in the follo

wing 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 AssertTest

10.

11. 4. {

12.

13. 5. private HashMap cctld;

14.

15. 6.

16.

17. 7. public AssertTest()

19. 8. {

20. 21. 9. cctld = new HashMap(); 22.

23. 10. cctld.put("in", "India"); 24.

25. 11. cctld.put("uk", "United Kingdom");

26.

27. 12. cctld.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 compile

B."Some things are true in this world" will be printed

C."Hey this won't compile" will be printed

D.None of these

4:A class design requires that a member variable should be accessible only by same package, which modifer word should be used?

A.protected

B.public

C.no modifer

D.private

5:Which is the main() method return of a application?

A.String

B.byte

C.char

D.void

6: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 out of memory

B.A program can suggest that garbage collection be performed and force it

C.Garbage collection is platform independent

D.An object becomes eligible for garbage collection when all references denoting it are set to null.

11: 1. What results from attempting to compile and run the following code? 2.

3. public class Ternary

4. 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 - 9

pilation error

C. prints: Value is - 5

D.None of these

12:

1. Give the following java source fragement:

2. //point x

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