装饰器模式

public class Competitor {
 
    public void sing()
 
    {
 
        System.out.println("我唱唱唱......");
 
    }
 
}

public class CompetitorDecorator1 extends Competitor {
    public void sing()
    {
        this.dance();
        super.sing();
    }
    private void dance()
    {
        System.out.println("偏偏起舞....");
    }
}

 

public class CompetitorDecorator2 extends Competitor {
    public void sing()
    {
        this.playMusic();
        super.sing();
    }
    private void playMusic()
    {
        System.out.println("播放背景音乐......");
    }
}

 

publicclass CompetitorDecorator3 extends Competitor {
    public void sing()
    {
        super.sing();
        this.introduceBackground();
    }
    private void introduceBackground()
    {
        System.out.println("悲惨背景介绍，博取同情，赢感情牌....");
    }
}
 

是的，这样确实可以完成相应的功能。但是有没有觉得怪怪的呢?

           1.我们在CompetitorDecorator2内已经有了 playMusic() 代码片段，我们在CompetitorDecorator4内有和它完全一样的playMusic()代码片段，这个是不合适的，也是不可取的！

           2.如果这个选手比较有才，有五花八门的各种装饰，我们为此要增加相应多的装饰类；如果他在这方面有很深的造诣，把这些装饰发挥的淋漓尽致，能把这些装饰融合到一块，这些五花八门的装饰随机组合，这得要衍生多少个子类啊!!!!!

           我们一般性地算一下，如果有不同的装饰功能 N 个，那么，如果我们将这N个随机组合，将有：

         

           也就是说做多可以产生sum 个子类，相信学过排列组合的人知道这是个什么概念，另外有多么庞大的代码重复……

装饰器

public class CompetitorDecorator extends Competitor{
 
    private Competitor competitor;
 
    public CompetitorDecorator(Competitor competitor)
    {
        this.competitor= competitor;
    }
    public void sing()
    {
        competitor.sing();
    }
}

 

public class CompetitorDecoratorA extends CompetitorDecorator {
    public CompetitorDecoratorA(Competitor competitor) {
        super(competitor);
    }
    public void sing()
    {
        this.dance();
        super.sing();
    }
    private void dance()
    {
        System.out.println("偏偏起舞....");
    }
 
}

 ———————————————— 

public class CompetitorDecoratorB extends CompetitorDecorator {
    public CompetitorDecoratorB(Competitor competitor) {
        super(competitor);
    }
    public void sing()
    {
        this.playMusic();
        super.sing();
    }
    private void playMusic()
    {
        System.out.println("播放背景音乐......");
    }
}
 ———————————————— 

public class CompetitorDecoratorC extends CompetitorDecorator {
    public CompetitorDecoratorC(Competitor competitor) {
        super(competitor);
    }
    publi cvoid sing()
    {
        super.sing();
        this.introduceBackground();
    }
    private void introduceBackground()
    {
        System.out.println("悲惨背景介绍，博取同情，赢感情牌....");
    }
}
 

public class Client {
 
    public static void main(String[] args) {
 
        Competitor com = new Competitor();
 
        // 加入了跳舞修饰，decorator 的sing() 方法中被动态添加了dance 修饰
 
        CompetitorDecorator decorator = new CompetitorDecoratorA(com);
 
        // 在上面修饰的基础上，加入背景音乐修饰
 
        decorator = new CompetitorDecoratorB(decorator);
 
        // 在上面修饰的基础上，加上悲惨的身世介绍
 
        decorator = new CompetitorDecoratorC(decorator);
 
        decorator.sing();
 
        System.out.println("满场尖叫，满分通过！！！！！");
 
    }
 
}