什么时候回收垃圾
public class RJMould{


StringBuffer sb;

public static void main(String[] args)

{

RJMould rjm = new RJMould();

rjm.kansas();

}
public void kansas(){

sb = new StringBuffer( "Manchester ");//8
StringBuffer sb2 =sb;//9

String Buffer sb3 = new StringBuffer( "OK ");//10

sb = sb3;//11
sb3 = null;//12

sb2 = null; //13


}

}

垃圾回收机制上说当代码无法在被访问的时候，就开始回收，那么在12行的时候就开始了，但是在SCJP考试卷子上它确说是13行，希望高人指点。

[解决办法]
例子：
class Test{
String name;
Long id;

public EqualObject(String name, Long id) {
super();
this.name = name;
this.id = id;
}

protected void finalize() throws Throwable {
System.out.println( "finalize( " + name + ", " + id + ") ");
}
}
public class MyTest{
public static void main(String[] args) {
EqualObject a = new Test( "1 ", new Long(1));
a = new Test( "2 ", new Long(2));
a = new Test( "3 ", new Long(3));
a = new Test( "4 ", new Long(4));
System.gc(); //如果没有这句，没有打印

a= null;
a = new Test( "5 ", new Long(5));
a= null;
a = new Test( "6 ", new Long(6));
a= null;
a = new Test( "7 ", new Long(7));
a= null;
System.gc(); //同上
}
}
[解决办法]
1.gc很懒
2.gc线程优先级低