flyweightfactorysingleton.java

《Java与模式》一书的源代码

package com.javapatterns.flyweight.simple;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class FlyweightFactorySingleton
{
    private HashMap flies = new HashMap();
    private static FlyweightFactorySingleton myself =
    new FlyweightFactorySingleton();

    private FlyweightFactorySingleton() { }

    public static FlyweightFactorySingleton getInstance()
    {
        return myself;
    }

    public Flyweight factory(Character state)
    {
        if (flies.containsKey(state))
        {
            return (Flyweight)flies.get(state);
        }
        else
        {
            Flyweight fly = new ConcreteFlyweight(state);
            flies.put(state, fly);
            return fly;
        }
    }

    public void checkFlyweight()
    {
        Flyweight fly = null;
        int i = 0;

        System.out.println("\n==========checkFlyweight()=============");
        for (Iterator it = flies.entrySet().iterator(); it.hasNext(); )
        {
            Map.Entry e = (Map.Entry) it.next();
            System.out.println("Item " + (++i) + " : " + e.getKey());
        }
        System.out.println("==========checkFlyweight()=============");
    }

}