3. 行为型模式 (2) 模板方法模式

3. 行为型模式 (2) 模板方法模式

在模板模式（Template Pattern）中，一个抽象类公开定义了执行它的方法的方式/模板。它的子类可以按需要重写方法实现，但调用将以抽象类中定义的方式进行。

优点：
1. 封装不变部分，扩展可变部分。
2. 提取公共代码，便于维护。
3. 行为由父类控制，子类实现。

缺点：
1. 每一个不同的实现都需要一个子类来实现，导致类的个数增加，使得系统更加庞大。

1. 模板方法模式

package com.andrew.pattern0302.template.model01;
public abstract class Game {
    abstract void initalize();
    abstract void startPlay();
    abstract void endPlay();
    // 模板
    public final void play() {
        initalize();
        startPlay();
        endPlay();
    }
}

package com.andrew.pattern0302.template.model01;
public class Cricket extends Game {
    @Override
    void initalize() {
        System.out.println("Cricket Game Initialized! Start playing.");
    }
    @Override
    void startPlay() {
        System.out.println("Cricket Game Started. Enjoy the game!");
    }
    @Override
    void endPlay() {
        System.out.println("Cricket Game Finished!");
    }
}

package com.andrew.pattern0302.template.model01;
public class Football extends Game {
    @Override
    void initalize() {
        System.out.println("Football Game Initialized! Start playing.");
    }
    @Override
    void startPlay() {
        System.out.println("Football Game Started. Enjoy the game!");
    }
    @Override
    void endPlay() {
        System.out.println("Football Game Finished!");
    }
}

package com.andrew.pattern0302.template.model01;
/**
 * 1. 模板模式
 * 
 * @author andrew
 * @date 2018/08/15
 */
public class Client {
    public static void main(String[] args) {
        Game game = new Cricket();
        game.play();
        System.out.println();
        game = new Football();
        game.play();
    }
}
运行结果：
Cricket Game Initialized! Start playing.
Cricket Game Started. Enjoy the game!
Cricket Game Finished!

Football Game Initialized! Start playing.
Football Game Started. Enjoy the game!
Football Game Finished!