72 lines
1.6 KiB
Java
72 lines
1.6 KiB
Java
// polymorphism/ReferenceCounting.java
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// (c)2017 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://OnJava8.com for more book information.
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// Cleaning up shared member objects
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class Shared {
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private int refcount = 0;
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private static long counter = 0;
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private final long id = counter++;
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Shared() {
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System.out.println("Creating " + this);
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}
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public void addRef() { refcount++; }
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protected void dispose() {
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if(--refcount == 0)
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System.out.println("Disposing " + this);
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}
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@Override
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public String toString() {
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return "Shared " + id;
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}
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}
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class Composing {
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private Shared shared;
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private static long counter = 0;
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private final long id = counter++;
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Composing(Shared shared) {
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System.out.println("Creating " + this);
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this.shared = shared;
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this.shared.addRef();
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}
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protected void dispose() {
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System.out.println("disposing " + this);
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shared.dispose();
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}
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@Override
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public String toString() {
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return "Composing " + id;
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}
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}
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public class ReferenceCounting {
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public static void main(String[] args) {
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Shared shared = new Shared();
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Composing[] composing = {
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new Composing(shared),
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new Composing(shared),
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new Composing(shared),
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new Composing(shared),
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new Composing(shared)
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};
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for(Composing c : composing)
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c.dispose();
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}
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}
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/* Output:
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Creating Shared 0
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Creating Composing 0
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Creating Composing 1
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Creating Composing 2
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Creating Composing 3
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Creating Composing 4
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disposing Composing 0
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disposing Composing 1
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disposing Composing 2
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disposing Composing 3
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disposing Composing 4
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Disposing Shared 0
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*/
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