使用”引用计数”跟踪仍旧访问着共享对象的对象数量
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);
}
public String
toString(){
return "Shared"+id;
}
}
class Composing{
private Shared shared;
private static long counter=
0;
private final
long id=counter++;
public Composing(Shared shared){
System.
out.println(
"Creating"+
this);
this.shared=shared;
this.shared.addRef();
}
protected void dispose(){
System.
out.println(
"disposing"+
this);
shared.disposing();
}
public String
toString(){
return "Composing"+id;}
}
public class ReferenceCounting{
public static void main(String[] args){
Shared shared=
new Shared();
Composing[] composing={
new Composing(shared);
new Composing(shared);
new Composing(shared);
new Composing(shared);
}
for(Composing c:composing)
c.dispose();
}
}
