package polymorphism;
/**
* 跟踪共享对象调用的数量
*/
public class ReferenceCounting {
public static void main(String[] args) {
Shared shared = new Shared();
Compsing[] compsings = {new Compsing(shared), new Compsing(shared), new Compsing(shared),
new Compsing(shared), new Compsing(shared)};
for (Compsing c : compsings)
c.dispose();
}
}
class Shared {
//参考数量
private int refcount = 0;
//统计实例创建的数量
private static long counter = 0;
//每创建一次实例就记一次数
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);
}
public String toString() {
return "Shared " + id;
}
}
class Compsing {
private Shared shared;
private static long counter = 0;
private final long id = counter++;
public Compsing(Shared shared) {
System.out.println(this);
System.out.println("Creatting" + this);
this.shared = shared;
this.shared.addRef();
}
protected void dispose() {
System.out.println("dispose" + this);
shared.dispose();
}
public String toString() {
return "Compsing" + id;
}
}
说实话这段代码看着都有点似懂非懂的感觉，虽然读懂是什么意思～ 但是不知道为什么这样设计，勉强理解！
