装饰器模式(Decorator)

//InputStream提供的基本方法(Component)
public abstract class InputStream implements Closeable {

}

//默认目标实现类(ConcreteComponent)
public class FileInputStream extends InputStream {

}

/*装饰实现类（FilterInputStream）一定是继承或实现原始接口(InputStream)的，内部有包含一个原始接口的超类(其实就是某个默认目标实现类)*/
//Decorator
public class FilterInputStream extends InputStream {
    /**
     * The input stream to be filtered.
     */
    protected volatile InputStream in;

    protected FilterInputStream(InputStream in) {
        this.in = in;
    }
}

//具体装饰类(ConcreteDecorator)
public class BufferedInputStream extends FilterInputStream {

    public BufferedInputStream(InputStream in) {
        this(in, DEFAULT_BUFFER_SIZE);
    }
}

//具体装饰类(ConcreteDecorator)
public class DataInputStream extends FilterInputStream implements DataInput {

    public DataInputStream(InputStream in) {
        super(in);
    }
}

package com.qbz.test;

interface ICoffee {
    void showCoffee();

    float showPrice();
}

// 原始咖啡
class Coffee implements ICoffee {
    private String name;
    private float price;

    public Coffee(String name, float price) {
        this.name = name;
        this.price = price;
    }

    @Override
    public void showCoffee() {
        System.out.println(name + " coffee");
    }

    @Override
    public float showPrice() {
        return price;
    }
}

// 抽象装饰器
abstract class Decorator implements ICoffee {
    private ICoffee coffee;

    public void setCoffee(ICoffee coffee) {
        this.coffee = coffee;
    }

    @Override
    public void showCoffee() {
        coffee.showCoffee();
    }

    @Override
    public float showPrice() {
        return coffee.showPrice();
    }
}

// 加糖咖啡
class Sugar extends Decorator {
    @Override
    public void showCoffee() {
        System.out.println("加糖");
        super.showCoffee();
    }

    @Override
    public float showPrice() {
        return super.showPrice() + 5;
    }
}

// 加牛奶的咖啡
class SugarMilk extends Decorator {
    @Override
    public void showCoffee() {
        System.out.println("加糖、加牛奶");
        super.showCoffee();
    }

    @Override
    public float showPrice() {
        return super.showPrice() + 10;
    }
}

public class Main {

    public static void main(String[] args) {
        Coffee coffee = new Coffee("拿铁", 20);
        // 加糖
        Decorator sugar = new Sugar();
        sugar.setCoffee(coffee);
        sugar.showCoffee();
        System.out.println(sugar.showPrice());
        // 加糖,加牛奶的咖啡
        Decorator sugarmilk = new SugarMilk();
        sugarmilk.setCoffee(coffee);
        sugarmilk.showCoffee();
        System.out.println(sugarmilk.showPrice());
    }

}

加糖
拿铁 coffee
25.0
加糖、加牛奶
拿铁 coffee
30.0