FlyWeight设计模式

Question

我正在浏览一个我在网上发现的飞重模式的例子。

import java.util.Random;
import java.util.HashMap;

// A common interface for all players
interface Player
{
    public void assignWeapon(String weapon);
    public void mission();
}

// Terrorist must have weapon and mission
class Terrorist implements Player
{
    // Intrinsic Attribute
    private final String TASK;

    // Extrinsic Attribute
    private String weapon;

    public Terrorist()
    {
        TASK = "PLANT A BOMB";
    }
    public void assignWeapon(String weapon)
    {
        // Assign a weapon
        this.weapon = weapon;
    }
    public void mission()
    {
        //Work on the Mission
        System.out.println("Terrorist with weapon "
                        + weapon + "|" + " Task is " + TASK);
    }
}

// CounterTerrorist must have weapon and mission
class CounterTerrorist implements Player
{
    // Intrinsic Attribute
    private final String TASK;

    // Extrinsic Attribute
    private String weapon;

    public CounterTerrorist()
    {
        TASK = "DIFFUSE BOMB";
    }
    public void assignWeapon(String weapon)
    {
        this.weapon = weapon;
    }
    public void mission()
    {
        System.out.println("Counter Terrorist with weapon "
                        + weapon + "|" + " Task is " + TASK);
    }
}

// Claass used to get a playeer using HashMap (Returns
// an existing player if a player of given type exists.
// Else creates a new player and returns it.
class PlayerFactory
{
    /* HashMap stores the reference to the object
    of Terrorist(TS) or CounterTerrorist(CT). */
    private static HashMap <String, Player> hm =
                        new HashMap<String, Player>();

    // Method to get a player
    public static Player getPlayer(String type)
    {
        Player p = null;

        /* If an object for TS or CT has already been
        created simply return its reference */
        if (hm.containsKey(type))
                p = hm.get(type);
        else
        {
            /* create an object of TS/CT */
            switch(type)
            {
            case "Terrorist":
                System.out.println("Terrorist Created");
                p = new Terrorist();
                break;
            case "CounterTerrorist":
                System.out.println("Counter Terrorist Created");
                p = new CounterTerrorist();
                break;
            default :
                System.out.println("Unreachable code!");
            }

            // Once created insert it into the HashMap
            hm.put(type, p);
        }
        return p;
    }
}

// Driver class
public class CounterStrike
{
    // All player types and weopons (used by getRandPlayerType()
    // and getRandWeapon()
    private static String[] playerType =
                    {"Terrorist", "CounterTerrorist"};
    private static String[] weapons =
    {"AK-47", "Maverick", "Gut Knife", "Desert Eagle"};


    // Driver code
    public static void main(String args[])
    {
        /* Assume that we have a total of 10 players
        in the game. */
        for (int i = 0; i < 10; i++)
        {
            /* getPlayer() is called simply using the class
            name since the method is a static one */
            Player p = PlayerFactory.getPlayer(getRandPlayerType());

            /* Assign a weapon chosen randomly uniformly
            from the weapon array */
            p.assignWeapon(getRandWeapon());

            // Send this player on a mission
            p.mission();
        }
    }

    // Utility methods to get a random player type and
    // weapon
    public static String getRandPlayerType()
    {
        Random r = new Random();

        // Will return an integer between [0,2)
        int randInt = r.nextInt(playerType.length);

        // return the player stored at index 'randInt'
        return playerType[randInt];
    }
    public static String getRandWeapon()
    {
        Random r = new Random();

        // Will return an integer between [0,5)
        int randInt = r.nextInt(weapons.length);

        // Return the weapon stored at index 'randInt'
        return weapons[randInt];
    }
}

Implementation：这是在反击游戏中创造恐怖分子和打击恐怖分子的工具。所以我们有两个等级，一个是恐怖分子(T)，另一个是反恐(CT)。每当玩家想要武器时，我们都会给他分配武器。在任务中，恐怖分子的任务是放置炸弹，而反恐怖分子则必须扩散炸弹。

我相信这个例子是wrong.In这个代码对象保持不变，我们只是改变武器，如果一个新玩家进入游戏，每个人的武器的意志改变。我理解得对吗？谁能给我提供一个很好的飞行重量的例子。

Answer 1

你是对的，你的榜样是错误的。你只有两个玩家在hashmap (CT和Tero)。使用hashmap来存储两个必须播放的对象是非常简单的。

而且，由于您只有两次播放，并且正在更改它们的attribut，但实际上您正在更改所有player config :)

我要修改了一小部分示例证明这是错误的。我只需将播放器存储在一个数组中，然后重新打印它。

     System.out.println("reuse --------------------------");
    for(Player p : players){
        p.mission();
    }

这给了我流量输出：

    Terrorist Created
Terrorist with weapon Maverick| Task is PLANT A BOMB
Counter Terrorist Created
Counter Terrorist with weapon AK-47| Task is DIFFUSE BOMB
Terrorist with weapon AK-47| Task is PLANT A BOMB
Terrorist with weapon Maverick| Task is PLANT A BOMB
Terrorist with weapon Gut Knife| Task is PLANT A BOMB
Counter Terrorist with weapon Desert Eagle| Task is DIFFUSE BOMB
Terrorist with weapon Gut Knife| Task is PLANT A BOMB
Counter Terrorist with weapon Gut Knife| Task is DIFFUSE BOMB
Terrorist with weapon Maverick| Task is PLANT A BOMB
Terrorist with weapon Maverick| Task is PLANT A BOMB
reuse --------------------------
Terrorist with weapon Maverick| Task is PLANT A BOMB
Counter Terrorist with weapon Gut Knife| Task is DIFFUSE BOMB
Terrorist with weapon Maverick| Task is PLANT A BOMB
Terrorist with weapon Maverick| Task is PLANT A BOMB
Terrorist with weapon Maverick| Task is PLANT A BOMB
Counter Terrorist with weapon Gut Knife| Task is DIFFUSE BOMB
Terrorist with weapon Maverick| Task is PLANT A BOMB
Counter Terrorist with weapon Gut Knife| Task is DIFFUSE BOMB
Terrorist with weapon Maverick| Task is PLANT A BOMB
Terrorist with weapon Maverick| Task is PLANT A BOMB

你清楚地看到每支球队都是同样的武器(最后一次被选中)。

如果您想要一个很好的例子，请参考您的文章;) :) )类似于维基百科

主要是重用已经创建的配置。