SCJP題庫第140題

Given:

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. public class C{

2.   public void method3(){

3.     //more code here

4.   }

5. }

And given:

25. try{

26.   A a = new A();

27.   a.method1();

28. }catch(Exception e){

29.   System.out.print("an error occurred");

30. }

Which two statements are true if a NullPointerException is thrown on line 3 of class C? (Choose two.)

 

 

A. The application will crash.

B. The code on 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.

 

Ans: BE

 

解說:

當類別C中的第3行(method3)拋出NullPointerException 時

method3不正常結束後回到類別B的第4行(method2)，而method2並沒有處理這個例外而不正常結束，又回到類別A的method1方法，回到method1的呼叫者27行(E)，這個例外被28行的catch補捉到，執行第29行(B)