SCJP 1.6版考題 140

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.

解答

---

Ans: B E

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)