JAVA基础面试题-2-答案版

JAVA语言基础笔试题-2

Question 1

Given:

11.classA {

12. public void process() { System.out.print(“A “)} } 13. class B extends A {

14. public void process() throws RuntimeException { 15. super.process();

16. if (true) throw new RuntimeException(); 17. System.out.print(“B”) }}

18. public static void main(String[] args) { 19. try { ((A)new B()).process(); }

20. catch (Exception e) { System.out.print(“Exception “)} 21. }

What is the result?

A. Exception B. A Exception C. A Exception B D. A B Exception

E. Compilation fails because of an error in line 14. F. Compilation fails because of an error in line 19.

答案:B

考点:方法的重写(重写方法异常抛出部分的理解) 多态 异常处理 说明:

子类重写父类方法,不能抛出比父类方法更多的异常,但此处子类重写方法声明抛出了

RuntimeException,不算多抛,算是平抛,是可以的。

RuntimeException是Exception的子类,可以被Exception捕获。

Question 2 Given:

11. static class A {

12. void process() throws Exception { throw new Exception(); } 13. }

14. static class B extends A {

15. void process() { System.out.println(“B”)} 16. }

17. public static void main(String[] args) { 18 .A a=new B(); 19. a.process(); 20.}

What is the result? A. B

B. The code runs with no output.

C. An exception is thrown at runtime.

D. Compilation fails because of an error in line 15. E. Compilation fails because of an error in line 18. F. Compilation fails because of an error in line 19.

答案:F

考点:方法的重写(重写方法异常抛出部分的理解) 多态

静态内部类以及其实例的创建 说明:

19. a.process(); 是多态调用,调用的应该是类B的process方法,这个方法只是

允许抛出RuntimeException, 所以19行在理论上不需要进行异常相关处理,系统会自动抛出该异常,但是多态只是在运行时,系统方能识别,在编译的时候,系统还是按照类A的process方法来进行验证,所以出现错误,因为类A抛出的是检查异常,必须显式被捕获或者抛出。

Question 3 Given:

11. static classA {

12. void process() throws Exception { throw new Exception(); } 13. }

14. static class B extends A {

15. void process() { System.out.println(“B”); 16. }

17. public static void main(String[] args) { 18. new B().process(); 19. }

What is the result? A. B

B. The code runs with no output.

C. Compilation fails because of an error in line 12. D. Compilation fails because of an error in line 15. E. Compilation fails because of an error in line 18.

答案:A

考点:方法的重写(重写方法异常抛出部分的理解) 静态内部类以及其实例的创建

Question 4 Given: 84. try {

85. ResourceConnection con = resourceFactory.getConnection(); 86. Results r = con.query(“GET INFO FROM CUSTOMER”) 87. info = r.getData(); 88. con.close();

89. } catch (ResourceException re) { 90. errorLog.write(re.getMessage()); 91. }

92. return info;

Which is true if a ResourceException is thrown on line 86?

A. Line 92 will not execute.

B. The connection will not be retrieved in line 85.

C. The resource connection will not be closed on line 88.

D. The enclosing method will throw an exception to its caller.

答案:C

考点:try..catch结构的理解 异常的捕获和处理

说明:由于抛出的ResourceException, 能够被catch块捕获(标配), 所以异常在方法中就被

处理掉了,不会抛出该方法。

根据try块操作上规定,一旦抛出异常,抛出异常语句后续部分的try块语句将不再运行。

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