a=null;
1 public class C {
2
3 protected A webDigester = new A(" first one ");
4
5 public void test(){
6
7 A a;
8
9 a=webDigester;
10
11 a.add(" second ");
12
13 a=null;
14
15 webDigester.display();
16 //猜猜会打印出什么呢？
17 }
18 public static void main(String[] args) {
19
20 C c=new C();
21
22 c.test();
23 }
24
25 }
1 import java.util.ArrayList;
2
3
4 public class A {
5
6 public ArrayList<Object> al=new ArrayList<Object>();
7
8 public void display()
9 {
10 System.out.println("-----start-------");
11 for(Object o:al)
12 {
13 System.out.println(" ["+o.toString()+"] ");
14 }
15 System.out.println("-----end-------");
16 }
17
18 public A(String msg){
19 al.add(msg);
20 }
21
22 public void add(String msg){
23 al.add(msg);
24 }
25
26 public void distory()
27 {
28 al.clear();
29 }
30
31 }
