每天一道面试题：对象引用及垃圾回收

 1 public class Test {
 2     public static class A {
 3         private B ref;
 4         public void setB(B b) {
 5             ref = b;
 6         }
 7     }
 8     public static Class B {
 9         private A ref;
10         public void setA(A a) {
11             ref = a;
12         }
13     }
14     public static void main(String args[]) {
15     …
16         start();
17     ….
18     }
19     public static void start() { 
20         A a = new A();
21         B b = new B();
22         a.setB(b);
23         b = null; //
24         a = null;
25     …
26     }
27 }