OCJP 考试题

QUESTION 150

Click the Exhibit button. Given: ClassA a = new ClassA(); a.methodA(); What is the result?

A. Compilation fails.
B. ClassC is displayed.
C. The code runs with no output.
D. An exception is thrown at runtime.
Answer: D

问题出在第24行，classC还没有new一个，就直接用函数getValue()，NullPointerException会被抛出

public ClassC classC;该行代码没有new出来ClassC,空指针异常；

QUESTION 151 Given:

11. static void test() throwsRuntimeException {

12. try {

13. System.out.print("test");

14. throw new RuntimeException();

15. }

16. catch (Exception ex) { System.out.print("exception"); }

17. }

18. public static voidmain(String[] args) {

19. try { test(); }

20. catch (RuntimeException ex) {System.out.print("runtime "); }

21. System.out.print("end");

22. }

What is the result?

A.   test end

B.   Compilation fails.

C.   test runtime end

D.   test exception end

E.   A Throwable is thrown by mainat runtime.

Answer: D

QUESTION 152 Given:

1. public class Plant {

2. private String name;

3. public Plant(String name) {this.name = name; }

4. public String getName() { returnname; }

5. }

6. public class Tree extends Plant{

7. public void growFruit() { }

8. public void dropLeaves() { }

9. }

Which statement is true?

A.   The code will compile withoutchanges.

B.   The code will compile if publicTree() { Plant(); } is added to the Tree class.

C.   The code will compile if publicPlant() { Tree(); } is added to the Plant class.

D.   The code willcompile if public Plant() { this("fern"); } is added to the Plantclass.

E.   The code will compile if publicPlant() { Plant("fern"); } is added to the Plant class.

Answer: D

Section: (none)
Plant需要一个无参默认构造函数，因为子类带一个参数的构造函数

QUESTION 153

Given:

10. class Line {

11. public static class Point {}

12. }

13. 
    

14. class Triangle {

15. // insert code here

16. }

Which code, inserted at line 15, createsan instance of the Point class defined in Line?

A.   Point p = new Point();

B.   Line.Point p = newLine.Point();

C.   The Point class cannot beinstatiated at line 15.

D.   Line l = new Line() ; l.Point p= new l.Point();

Answer: B

QUESTION 154 Given:

10. class Nav{

11. public enum Direction { NORTH,SOUTH, EAST, WEST }

12. }

13. public class Sprite{

14. // insert code here

15. }

Which code, inserted at line 14, allowsthe Sprite class to compile?

A.   Direction d = NORTH;

B.   Nav.Direction d = NORTH;

C.   Direction d = Direction.NORTH;

D.   Nav.Direction d = Nav.Direction.NORTH;

Answer: D

Section: (none)