享元模式,以共享的方式高效地支持大量的细粒度对象。通过复用内存中已存在的对象,降低系统创建对象实例的性能消耗。享元的英文是Flyweight,表示特别小的对象,即细粒度对象。
我们借用五子棋游戏来说明这一模式。
UML
代码:
创建抽象棋子一AbstractChessman
package com.demo.flyweight.object;
public abstract class AbstractChessman {
// 棋子坐标
protected int x;
protected int y;
// 棋子类别(黑|白)
protected String chess;
public AbstractChessman(String chess) {
this.chess = chess;
}
// 点坐标设置
public abstract void point(int x, int y);
// 显示棋子信息
public void show() {
System.out.println(this.chess + "(" + this.x + "," + this.y + ")");
}
}
3.2 创建黑子一BlackChessman
package com.demo.flyweight.object;
public class BlackChessman extends AbstractChessman {
/**
* 构造方法 初始化黑棋子
*/
public BlackChessman() {
super("●");
System.out.println("--BlackChessman Construction Exec!!!");
}
// 点坐标设置
@Override
public void point(int x, int y) {
this.x = x;
this.y = y;
// 显示棋子内容
show();
}
}
3.3 创建白子一WhiteChessman
package com.demo.flyweight.object;
public class WhiteChessman extends AbstractChessman {
/**
* 构造方法 初始化白棋子
*/
public WhiteChessman() {
super("○");
System.out.println("--WhiteChessman Construction Exec!!!");
}
// 点坐标设置
@Override
public void point(int x, int y) {
this.x = x;
this.y = y;
// 显示棋子内容
show();
}
}
3.4 创建棋子工厂一FiveChessmanFactory
package com.demo.flyweight.factory;
import java.util.Hashtable;
import com.demo.flyweight.object.AbstractChessman;
import com.demo.flyweight.object.BlackChessman;
import com.demo.flyweight.object.WhiteChessman;
public class FiveChessmanFactory {
// 单例模式工厂
private static FiveChessmanFactory fiveChessmanFactory = new FiveChessmanFactory();
// 缓存存放共享对象
private final Hashtable<Character, AbstractChessman> cache = new Hashtable<Character, AbstractChessman>();
// 私有化构造方法
private FiveChessmanFactory() {
}
// 获得单例工厂
public static FiveChessmanFactory getInstance() {
return fiveChessmanFactory;
}
/**
* 根据字符获得棋子
*
* @param c
* (B:黑棋 W:白棋)
* @return
*/
public AbstractChessman getChessmanObject(char c) {
// 从缓存中获得棋子对象实例
AbstractChessman abstractChessman = this.cache.get(c);
if (abstractChessman == null) {
// 缓存中没有棋子对象实例信息 则创建棋子对象实例 并放入缓存
switch (c) {
case 'B':
abstractChessman = new BlackChessman();
break;
case 'W':
abstractChessman = new WhiteChessman();
break;
default:
break;
}
// 为防止 非法字符的进入 返回null
if (abstractChessman != null) {
// 放入缓存
this.cache.put(c, abstractChessman);
}
}
// 如果缓存中存在 棋子对象则直接返回
return abstractChessman;
}
}
3.5 客户端实现一Client
package com.demo;
import java.util.Random;
import com.demo.flyweight.factory.FiveChessmanFactory;
import com.demo.flyweight.object.AbstractChessman;
/**
* 主应用程序
*
* @author
*/
public class Client {
/**
* @param args
*/
public static void main(String[] args) {
// 创建五子棋工厂
FiveChessmanFactory fiveChessmanFactory = FiveChessmanFactory
.getInstance();
Random random = new Random();
int radom = 0;
AbstractChessman abstractChessman = null;
// 随机获得棋子
for (int i = 0; i < 10; i++) {
radom = random.nextInt(2);
switch (radom) {
// 获得黑棋
case 0:
abstractChessman = fiveChessmanFactory.getChessmanObject('B');
break;
// 获得白棋
case 1:
abstractChessman = fiveChessmanFactory.getChessmanObject('W');
break;
}
if (abstractChessman != null) {
abstractChessman.point(i, random.nextInt(15));
}
}
}
}
--WhiteChessman Construction Exec!!!
○(0,2)
○(1,6)
--BlackChessman Construction Exec!!!
●(2,3)
○(3,14)
○(4,13)
○(5,8)
●(6,14)
●(7,0)
●(8,3)
○(9,8)