GOF23设计模式（九）

GOF设计模式之享元模式(FlyWeight)

享元模式以共享的方式高效地支持大量细粒度对象的重用。
享元对象能做到共享的关键是区分了内部状态和外部状态
·内部状态：可以共享，不会随环境变化而改变
·外部状态：不可以共享，会随环境变化而改变

享元类

/**
 * 享元类
 */
public interface ChessFlyWeight {
	void setColor(String c);
	String getColor();
	void display(Coordinate c);
}

class ConcreteChess implements ChessFlyWeight{
	private String color;
	
	public ConcreteChess(String color) {
		this.color = color;
	}

	@Override
	public void setColor(String c) {
		this.color=c;
	}

	@Override
	public String getColor() {
		return color;
	}

	@Override
	public void display(Coordinate c) {
		System.out.println("棋子颜色"+color);
		System.out.println("棋子位置"+c.getX()+"-----"+c.getY());
	}	
}

外部状态

/**
 * 外部状态UnSharedConcreteFlayWeight
 */
public class Coordinate {
	private int x,y;

	public Coordinate(int x, int y) {
		this.x = x;
		this.y = y;
	}

	public int getX() {
		return x;
	}

	public void setX(int x) {
		this.x = x;
	}

	public int getY() {
		return y;
	}

	public void setY(int y) {
		this.y = y;
	}	
}

享元工厂

/**
 * 享元工厂
 *
 */
public class ChessFlyWeightFactory {
	//享元池
	private static Map<String,ChessFlyWeight> map=new HashMap<String,ChessFlyWeight>();
	
	public static  ChessFlyWeight getChess(String color) {
		if(map.get(color)!=null) {
			return map.get(color);
		}else {
			ChessFlyWeight cfw=new ConcreteChess(color);
			map.put(color,cfw);
			return cfw;
		}
	}
}

测试

public class Client {

	public static void main(String[] args) {
		ChessFlyWeight chess1=ChessFlyWeightFactory.getChess("黑色");
		ChessFlyWeight chess2=ChessFlyWeightFactory.getChess("黑色");
		System.out.println(chess1);
		System.out.println(chess2);
		System.out.println("外部状态处理");
		chess1.display(new Coordinate(12,5));
		chess2.display(new Coordinate(15,7));
	}
}

结果

FlyWeight.ConcreteChess@15db9742
FlyWeight.ConcreteChess@15db9742
外部状态处理
棋子颜色黑色
棋子位置12—–5
棋子颜色黑色
棋子位置15—–7