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Java 父类和子类对象销毁实例

2013-12-02 14:32 471 查看

1）定义一个共享类Shared

使用long而不使用int，是为了防止溢出，refcount是共享类被其他类引用的次数，只要还有其他的类引用这个类，共享类就不会被GC回收。

package cn.javass.user;

public class Shared {

private int refcount=0;

private static long counter=0;

private final long id=counter++;

public Shared(){

System.out.println("Creating "+this);

}

public void addRef(){refcount++;};

protected void dispose(){

if(--refcount==0){

System.out.println("Disposing "+this);

}

}

//重写toString方法

public String toString(){return "Shared"+id;};

}

2)定义一个组合类

package cn.javass.user;

public class Composing {

private Shared shared;

private static long counter=0;

private final long id=counter++;

public Composing(Shared shared) {

// TODO Auto-generated constructor stub

System.out.println("Creating "+this);

this.shared=shared;

this.shared.addRef();

}

protected void dispose(){

System.out.println("disposing "+this);

shared.dispose();

}

public String toString(){return "Composing" +id; };

}

3）定义引用计数类

package cn.javass.user;

public class ReferenceCounting {

public static void main(String[] args) {

Shared shared=new Shared();

Composing[] composings={new Composing(shared),new Composing(shared),new Composing(shared),new Composing(shared),new Composing(shared)};

for(Composing c:composings)

c.dispose();

}

}

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