Java设计模式之java装饰者模式详解

目录

• 介绍
• 角色
• 示例代码
• 星巴克咖啡的例子
  • 方案一
  • 方案二 ：将调料内置到Drink类中
  • 方案三:装饰者模式
    • 代码演示
• 装饰者模式的简化
• 透明性的要求
• 半透明的装饰模式
• 装饰模式的优点
• 装饰模式的缺点
• 装饰模式注意事项
• 适用场景
• 设计模式在JAVA I/O库中的应用
• 透明和半透明的装饰模式的区别
• 参考文章
• 总结

public interface Component {
    public void sampleOperation();
}

public class ConcreteComponent implements Component {
    @Override
    public void sampleOperation() {
        // 写相关的业务代码
    }
}

public class Decorator implements Component{
    private Component component;
    public Decorator(Component component){
        this.component = component;
    }
    @Override
    public void sampleOperation() {
        // 委派给构件
        component.sampleOperation();
    }
}

public class ConcreteDecoratorA extends Decorator {
    public ConcreteDecoratorA(Component component) {
        super(component);
    }
    @Override
    public void sampleOperation() {
　　　　　super.sampleOperation();
        // 写相关的业务代码
    }
}

public class ConcreteDecoratorB extends Decorator {
    public ConcreteDecoratorB(Component component) {
        super(component);
    }
    @Override
    public void sampleOperation() {
　　　　  super.sampleOperation();
        // 写相关的业务代码
    }
}

public abstract class Drink
{
   protected String decription="";//描述
   public String getDecription() {
      return decription;
   }
   public abstract Integer cost();//返回饮料的价格
}

//缓冲层----所有种类咖啡的共同点抽取出来
public abstract class Coffee extends Drink
{
    //共同特点：计算价格
    @Override
    public Integer cost() {
        //价格从0累加
        return 0;
    }
}

public class LongBlack extends Coffee
{
    LongBlack()
    {
        decription="美式咖啡";
    }
    @Override
    public Integer cost() {
        return 15;
    }
}

public class ChinaBlack extends Coffee
{
    ChinaBlack()
    {
        decription="中式咖啡";
    }
    @Override
    public Integer cost() {
        return 10;
    }
}

public class Espresso extends Coffee
{
    //设置描述信息
    Espresso()
    {
        decription="意大利咖啡";
    }
    @Override
    public Integer cost() {
        //意大利咖啡20元
        return 20;
    }
}

//装饰者
public abstract class Decorator extends Drink
{
    @Override
    public abstract String getDecription();
}

public class Milk extends Decorator{
    Drink drink;
    Milk(Drink drink)
    {
        this.drink=drink;
    }
    @Override
    public String getDecription()
    {
        return "加了牛奶的"+this.drink.getDecription();
    }
    @Override
    public Integer cost()
    {
        return this.drink.cost()+3;
    }
}

public class Chocolate extends Decorator{
     //用一个实例变量记录饮料，也就是被装饰者
    Drink drink;
    Chocolate(Drink drink) {
       this.drink=drink;
    }
    @Override
    public String getDecription() {
        return "加了巧克力的"+drink.getDecription();
    }
    @Override
    public Integer cost() {
        //在原有饮料价格的基础上加上调料味的价格
        return 5+drink.cost();
    }
}

public class test
{
    @Test
    public void test()
    {
        //模拟下单
        //首先点一个美式咖啡，不加任何调料
        Drink drink=new LongBlack();
        System.out.println("购买了"+drink.getDecription()+"  花了"+drink.cost());
        //给美式咖啡加一个巧克力
        drink=new Chocolate(drink);
        System.out.println("购买了"+drink.getDecription()+"  花了"+drink.cost());
        //给美式咖啡再加一个牛奶
        drink=new Milk(drink);
        System.out.println("购买了"+drink.getDecription()+"  花了"+drink.cost());
        //再把牛奶和巧克力加一次
        drink=new Chocolate(drink);
        System.out.println("购买了"+drink.getDecription()+"  花了"+drink.cost());
        drink=new Milk(drink);
        System.out.println("购买了"+drink.getDecription()+"  花了"+drink.cost());
        System.out.println("====================================================");
        //简化写法
        Drink d=new Chocolate(new Milk(new ChinaBlack()));
        System.out.println("购买了"+d.getDecription()+"  花了"+d.cost());
    }
}

Drink drink=new LongBlack();
//给美式咖啡加一个巧克力
drink=new Chocolate(drink);

Drink drink=new LongBlack();
//给美式咖啡加一个巧克力
Chocolate drink=new Chocolate(drink);

Drink drink=new LongBlack();
//给美式咖啡加一个巧克力
Chocolate drink=new Chocolate(drink);
//售卖巧克力棒
drink.sell();

public class IOTest {
    public static void main(String[] args) throws IOException {
        // 流式读取文件
        DataInputStream dis = null;
        try{
            dis = new DataInputStream(
                    new BufferedInputStream(
                            new FileInputStream("test.txt")
                    )
            );
            //读取文件内容
            byte[] bs = new byte[dis.available()];
            dis.read(bs);
            String content = new String(bs);
            System.out.println(content);
        }finally{
            dis.close();
        }
    }
}