享元模式实例五子棋

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

代码语言：javascript复制

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

代码语言：javascript复制

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

代码语言：javascript复制

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

代码语言：javascript复制

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

代码语言：javascript复制

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));
      }
    }
  }
}

1. 运行结果

代码语言：javascript复制

--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)

uml abstract

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