享元模式

场景：如果有很多个完全相同或者相似的对象，我们可以通过享元模式，节省内存。

核心：享元模式以共享方式高效的支持大量细粒度对象重用

应用场景；任何池，String类

例子：比如围棋中，有黑棋白棋，同种颜色的棋子，只有坐标不一样，其他都一样，这是就可以用享元模式

Coordinate.java（外部状态）

public class Coordinate {private int x,y;public Coordinate(int x, int y) {super();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;}}

ChessFlyWeight.java（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) {super();this.color = color;}@Overridepublic void display(Coordinate c) {System.out.println("棋子颜色："+color);System.out.println("棋子位置："+c.getX()+"----"+c.getY());}@Overridepublic String getColor() {return color;}@Overridepublic void setColor(String c) {this.color = c;}}

ChessFlyWeightFactory.java（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;}}}

测试类

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("增加外部状态的处理===========");chess1.display(new Coordinate(10, 10));chess2.display(new Coordinate(20, 20));}}