装饰者模式

引言

还是以热干面，加鸡蛋的热干面，加牛肉的热干面举例子

代码如下

1.先创建一个面条的接口

public interface Noodle {

    public String getNoodleName();

    public Double getNoodlePrice();
}

写一些具体的类去实现面条，比如说热干面

public class HotDryNoodle implements Noodle{

    @Override
    public String getNoodleName() {
        return "热干面";
    }

    @Override
    public Double getNoodlePrice() {
        return 4.0;
    }

}

然后此时写一个面条的装饰器，这个装饰器应该实现有参的构造方法，传入什么面条就行，在面条的基础上加东西。

public abstract class NoodleDecorator implements Noodle{

    public Noodle noodle;

    public NoodleDecorator(Noodle noodle) {
        this.noodle = noodle;
    }

}

现在可以写加鸡蛋的热干面，加牛肉的热干面了

public class AddBeafNoodle extends NoodleDecorator {

    public AddBeafNoodle(Noodle noodle) {
        super(noodle);
    }

    @Override
    public String getNoodleName() {
        return noodle.getNoodleName()+"加牛肉";
    }

    @Override
    public Double getNoodlePrice() {
        return noodle.getNoodlePrice()+5.0;
    }

}

public class AddEggNoodle extends NoodleDecorator{

    public AddEggNoodle(Noodle noodle) {
        super(noodle);
    }

    @Override
    public String getNoodleName() {
        return noodle.getNoodleName()+"加鸡蛋";
    }

    @Override
    public Double getNoodlePrice() {
        return noodle.getNoodlePrice()+2.0;
    }

}

测试

public class TestMain {

    public static void main(String[] args) {
        HotDryNoodle hotDryNoodle = new HotDryNoodle();

        AddEggNoodle eggNoodle = new AddEggNoodle(hotDryNoodle);
        System.out.println(eggNoodle.getNoodleName());
        System.out.println(eggNoodle.getNoodlePrice());

        AddBeafNoodle beafNoodle = new AddBeafNoodle(hotDryNoodle);
        System.out.println(beafNoodle.getNoodleName());
        System.out.println(beafNoodle.getNoodlePrice());

        AddBeafNoodle beafAndEggNoodle = new AddBeafNoodle(new AddEggNoodle(hotDryNoodle));
        System.out.println(beafAndEggNoodle.getNoodleName());
        System.out.println(beafAndEggNoodle.getNoodlePrice());
    }
}