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  • Java设计模式(三) 装饰模式

    装饰模式:动态的将责任附加到对象上,想要扩展功能,装饰者提供有别于继承的另一种选择。

    1,创建顶级类

    package com.pattern.decorate;
    
    public abstract class Beverage {
    	
    	String description = "Unknown Beverage";
    	
    	public String getDescription(){
    		return description;
    	}
    	
    	public abstract double cost();
    }

    2,创建产品类

    package com.pattern.decorate;
    
    public class Espresso extends Beverage{
    	
    	public Espresso(){
    		description = "Espresso";
    	}
    	/** 
    	 * @see com.pattern.decorate.Beverage#cost()
    	 */
    	@Override
    	public double cost() {
    		return 1.99;
    	}
    }
    package com.pattern.decorate;
    
    public class HouseBlend extends Beverage{
    
    	public HouseBlend(){
    		description = "House Blend Coffee";
    	}
    	
    	/** 
    	 * @see com.pattern.decorate.Beverage#cost()
    	 */
    	@Override
    	public double cost() {
    		return .89;
    	}
    
    }
    package com.pattern.decorate;
    
    public class DarkRoast extends Beverage {
    
    	public DarkRoast(){
    		description = "DarkRoast";
    	}
    	/** 
    	 * @see com.pattern.decorate.Beverage#cost()
    	 */
    	@Override
    	public double cost() {
    		return 2.99;
    	}
    
    }

    3,创建装饰类

    package com.pattern.decorate;
    
    public abstract class CondimentDecorator extends Beverage{
    	
    	public abstract String getDescription();
    }


    4,创建装饰类的具体实现类

    package com.pattern.decorate;
    
    public  class Whip extends CondimentDecorator {
    	
    	public Beverage beverage;
    
    	public Whip(Beverage beverage) {
    		this.beverage = beverage;
    	}
    
    	/** 
    	 * @see com.pattern.decorate.CondimentDecorator#getDescription()
    	 */
    	@Override
    	public String getDescription() {
    		return beverage.getDescription()+", Whip";
    	}
    
    	/** 
    	 * @see com.pattern.decorate.Beverage#cost()
    	 */
    	@Override
    	public double cost() {
    		return .30+beverage.cost();
    	}
    
    }
    
    package com.pattern.decorate;
    
    public class Mocha extends CondimentDecorator{
    
    	Beverage beverage;
    	
    	public Mocha(Beverage beverage){
    		this.beverage = beverage;
    	}
    	
    	/** 
    	 * @see com.pattern.decorate.CondimentDecorator#getDescription()
    	 */
    	@Override
    	public String getDescription() {
    		return beverage.getDescription()+", Mocha";
    	}
    
    	/** 
    	 * @see com.pattern.decorate.Beverage#cost()
    	 */
    	@Override
    	public double cost() {
    		return .20+beverage.cost();
    	}
    
    }
    

    5,测试

    package com.pattern.decorate;
    
    public class StarbuzzCoffee {
    	
    	public static void main(String[] args) {
    		Beverage beverage = new Espresso();
    		System.out.println(beverage.getDescription()+" $"+beverage.cost());
    		
    		Beverage beverage2 = new DarkRoast();
    		beverage2 = new Mocha(beverage2);
    		beverage2 = new Mocha(beverage2);
    		beverage2 = new Whip(beverage2);
    		System.out.println(beverage2.getDescription()+" $"+beverage2.cost());
    	}
    }
    

    上图装饰类与被装饰类 具有共同的父类。

    其实也可以不具有相同的父类!




     

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  • 原文地址:https://www.cnblogs.com/mengjianzhou/p/5986820.html
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