23种设计模式（21）-享元模式

public class Test {
    public static void main(String[] args) {
        String a = "abc";
        String b = "abc";
        System.out.println(a==b);
    }
}

public interface Flyweight {
    //一个示意性方法，参数state是外蕴状态
    public void operation(String state);
}

public class ConcreteFlyweight implements Flyweight {
    private Character intrinsicState = null;
    /**
     * 构造函数，内蕴状态作为参数传入
     * @param state
     */
    public ConcreteFlyweight(Character state){
        this.intrinsicState = state;
    }
   
    /**
     * 外蕴状态作为参数传入方法中，改变方法的行为，
     * 但是并不改变对象的内蕴状态。
     */
    @Override
    public void operation(String state) {
        // TODO Auto-generated method stub
        System.out.println("Intrinsic State = " + this.intrinsicState);
        System.out.println("Extrinsic State = " + state);
    }
}

public class FlyweightFactory {
    private Map<Character,Flyweight> files = new HashMap<Character,Flyweight>();
    
    public Flyweight factory(Character state){
        //先从缓存中查找对象
        Flyweight fly = files.get(state);
        if(fly == null){
            //如果对象不存在则创建一个新的Flyweight对象
            fly = new ConcreteFlyweight(state);
            //把这个新的Flyweight对象添加到缓存中
            files.put(state, fly);
        }
        return fly;
    }
}

public class Client {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        FlyweightFactory factory = new FlyweightFactory();
        Flyweight fly = factory.factory(new Character('a'));
        fly.operation("First Call");
        
        fly = factory.factory(new Character('b'));
        fly.operation("Second Call");
        
        fly = factory.factory(new Character('a'));
        fly.operation("Third Call");
    }
}

public interface Flyweight {
    //一个示意性方法，参数state是外蕴状态
    public void operation(String state);
}

public class ConcreteFlyweight implements Flyweight {
    private Character intrinsicState = null;
    /**
     * 构造函数，内蕴状态作为参数传入
     * @param state
     */
    public ConcreteFlyweight(Character state){
        this.intrinsicState = state;
    }
    
    /**
     * 外蕴状态作为参数传入方法中，改变方法的行为，
     * 但是并不改变对象的内蕴状态。
     */
    @Override
    public void operation(String state) {
        // TODO Auto-generated method stub
        System.out.println("Intrinsic State = " + this.intrinsicState);
        System.out.println("Extrinsic State = " + state);
    }

}

public class ConcreteCompositeFlyweight implements Flyweight {
    
    private Map<Character,Flyweight> files = new HashMap<Character,Flyweight>();
    /**
     * 增加一个新的单纯享元对象到聚集中
     */
    public void add(Character key , Flyweight fly){
        files.put(key,fly);
    }
    /**
     * 外蕴状态作为参数传入到方法中
     */
    @Override
    public void operation(String state) {
        Flyweight fly = null;
        for(Object o : files.keySet()){
            fly = files.get(o);
            fly.operation(state);
        } 
    }
}

public class FlyweightFactory {
    private Map<Character,Flyweight> files = new HashMap<Character,Flyweight>();
    /**
     * 复合享元工厂方法
     */
    public Flyweight factory(List<Character> compositeState){
        ConcreteCompositeFlyweight compositeFly = new ConcreteCompositeFlyweight();
        
        for(Character state : compositeState){
            compositeFly.add(state,this.factory(state));
        }
        
        return compositeFly;
    }
    /**
     * 单纯享元工厂方法
     */
    public Flyweight factory(Character state){
        //先从缓存中查找对象
        Flyweight fly = files.get(state);
        if(fly == null){
            //如果对象不存在则创建一个新的Flyweight对象
            fly = new ConcreteFlyweight(state);
            //把这个新的Flyweight对象添加到缓存中
            files.put(state, fly);
        }
        return fly;
    }
}

public class Client {

    public static void main(String[] args) {
        List<Character> compositeState = new ArrayList<Character>();
        compositeState.add('a');
        compositeState.add('b');
        compositeState.add('c');
        compositeState.add('a');
        compositeState.add('b');
        
        FlyweightFactory flyFactory = new FlyweightFactory();
        Flyweight compositeFly1 = flyFactory.factory(compositeState);
        Flyweight compositeFly2 = flyFactory.factory(compositeState);
        compositeFly1.operation("Composite Call");
        
        System.out.println("---------------------------------");        
        System.out.println("复合享元模式是否可以共享对象：" + (compositeFly1 == compositeFly2));
        
        Character state = 'a';
        Flyweight fly1 = flyFactory.factory(state);
        Flyweight fly2 = flyFactory.factory(state);
        System.out.println("单纯享元模式是否可以共享对象：" + (fly1 == fly2));
    }
}