設計模式之裝飾模式（Decorator）

場景

普通人跑步，跳高，舉重很普通。
現在需要使用裝備變成鋼鐵俠，3項指標成倍擴大

Man介面

public interface Man {

    void run();

    int highJump();

    int weightlifting();
}

normal man

public class NormalMan implements Man {
    @Override
    public void run() {
        System.out.println(
 
"Normal man run.");
    }

    @Override
    public int highJump() {
        System.out.println("Normal man heigh jump 1m.");
        return 1;
    }

    @Override
    public int weightlifting() {
        System.out.println("Normal man weightlifting 30KG.");
        return 30;
    }
}

iron man

public
 
 class IronMan implements Man {

    private Man normalMan;

    public IronMan(Man normalMan) {
        this.normalMan = normalMan;
    }

    @Override
    public void run() {
        normalMan.run();
        System.out.println("upgrade iron man speed 1000m/s");
    }

    @Override
    public int highJump
 
() {
        System.out.println("upgrade iron man highJump "+normalMan.highJump()*100+"m.");
        return normalMan.highJump()*100;
    }

    @Override
    public int weightlifting() {
        System.out.println("upgrade iron man weightlifting "+normalMan.weightlifting()*100+" KG");
        return normalMan.weightlifting()*100;
    }
}

測試

 @Test
    public void decorator(){
        Man normalMan = new NormalMan();
        normalMan.run();
        normalMan.highJump();
        normalMan.weightlifting();

        System.out.println("==============");
        Man ironMan = new IronMan(normalMan);
        ironMan.run();
        ironMan.highJump();
        ironMan.weightlifting();
    }

類圖

適用性

• 動態且透明地向各個物件新增職責，即不影響其他物件

• 對於可以撤回的責任
• 通過子類擴充套件是不切實際的。有時可能會有大量獨立擴充套件，並會產生大量子類以支援每種組合。或者類定義可能隱藏或不可用於子類化