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1、JAVA语言基础笔试题-2Question 1Given: 11.classA “A “) 13. class B extends A 14. public void process() throws RuntimeException 15. super.process(); 16. if (true) throw new RuntimeException(); “B”) 18. public static void main(String args) 19. try (A)new B().process(); “Exception “) 21. What is the result? A.
2、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Exceptio
3、n的子类，可以被Exception捕获。Question 2Given: 11. static class A 12. void process() throws Exception throw new Exception(); 13. 14. static class B extends A 15. void ) 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.
4、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Runt
5、imeException, 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 3Given: 11. static classA 12. void process() throws Exception throw new Exception(); 13. 14. static class B extends A “B”); 16. 17. public static void main(String a
6、rgs) 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 4G
7、iven: 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 thr
8、own 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
9、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。Question 5Click the Exhibit button. 1. public class A 2. public void method1() 3. B b= new B(); 4. b.method2(); 5. / more code here 6. 7. 1. public class B 2. public void method2() 3. C c=new C(); 4. c.method3(); 5. / more code here 6. 7. 1.
10、public class C 2. public void method3() 3. / more code here 4. 5. Given: 25. try 26. A a=new A(); 27. a.method1(); 28. catch (Exception e) “an error occurred!”)30. Which two are true if a NullPointerException is thrown on line 3 of class C? (Choose two.) A. The application will crash. B. The code on
11、 line 29 will be executed. C. The code on line 5 of class A will execute. D. The code on line 5 of class B will execute. E. The exception will be propagated back to line 27. 答案：BE考点：异常的抛出、捕获和处理说明： 一般来说，异常的抛出，最终终将被处理，本方法不处理，则抛给主调方法，关键是要能抛的出去，因为NullpointerException是RuntimeException,所以一路没有阻碍，最终propagat
12、ed back 到达27行，Exception是所有异常的父类，所以该异常在这里被处理了，Question 6Click the Exhibit button. 1. public class A 2. public void method1() 3. try 4. B b=new B(); 5. b.method2(); 6. / more code here 7. catch (TestException te) 8. throw new RuntimeException(te); 9. 6. 7. 1. public class B 2. public void method2() th
13、rows TestException 3. / more code here 4. 5. 1. public class TestException extends Exception 2. Given: 31. public void method() 32. A a=new A(); 33. a.method1(); 34. Which is true if a TestException is thrown on line 3 of class B? A. Line 33 must be called within a try block. B. The exception thrown
14、 by method1 in class A is not required to be caught. C. The method declared on line 31 must be declared to throw a RuntimeException. D. On line 5 of class A, the call to method2 of class B does not need to be placed in a try/catch block. 答案：B考点：异常抛出、捕获和处理说明： 第8行，把检查异常TestException封装在RuntimeException中抛出是可以，因为系统仍然认为你抛出的是一个运行时异常，任何方法都默认支持抛出运行时异常。Question 7Given: 11. public static void main(String args) 12. try 13. args=null; 14. args0 =”test”;16. catch (Exception ex) “Exception”)18. catch (NullPoi
