设计模式之装饰器

案例：

咖啡馆订单：

1）、咖啡种类：Espresso、ShortBlack、LongBlack、Decaf

2）、调料：Milk、Soy、Chocolate

3）、扩展性好、改动方便、维护方便

类图：



关键代码：

装饰者模式下的订单：2份巧克力+一份牛奶的LongBlack

1. Component
package CoffeeBar.AbstractSuperClass;

public abstract class Drink
{
public String description="";
private float price=0.f;

public abstract float cost();

public String getDescription()
{
return description+"-"+getPrice();
}
public void setDescription(String description)
{
this.description = description;
}
public float getPrice()
{
return price;
}
public void setPrice(float price)
{
this.price = price;
}

}

2.  ConcreteComponent
package CoffeeBar.ConcreteComponent;

import CoffeeBar.AbstractSuperClass.Drink;

public class Coffee extends Drink
{

@Override
public float cost()
{
return super.getPrice();
}

}

package CoffeeBar.ConcreteComponent;

public class LongBlack extends Coffee
{
public LongBlack()
{
super.setDescription("LongBlack");
super.setPrice(6.0f);
System.out.println("LongBlack,6.0");
}
}

3. Decorator
package CoffeeBar.Decorator;

import CoffeeBar.AbstractSuperClass.Drink;

public class Decorator extends Drink
{
private Drink obj;

public Decorator(Drink obj)
{
this.obj=obj;
}

@Override
public float cost()
{
System.out.println("obj.getPrice()"+obj.getPrice());
System.out.println("super.getPrice()"+super.getPrice());
return super.getPrice()+obj.cost();
}

@Override
public String getDescription()
{
return super.description+super.getPrice()+"&&"+obj.getDescription();
}

}

4. ConcreteDecorator:
package CoffeeBar.Decorator;

import CoffeeBar.AbstractSuperClass.Drink;

public class Milk extends Decorator
{

public Milk(Drink obj)
{
super(obj);
super.setDescription("Milk");
super.setPrice(2.0f);
}

}

5. 入口
order=new LongBlack();
order=new Milk(order);
order=new Chocolate(order);
order=new Chocolate(order);
System.out.println("price:"+order.cost());
System.out.println("desc:"+order.getDescription());

装饰器模式原理：



实际应用案例

java 的IO流



自定义一个转大写的ConcoreateDecorator

package myjavaIO;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;

public class UpperCaseInputStream extends FilterInputStream
{

protected UpperCaseInputStream(InputStream in)
{
super(in);
}

public int read() throws IOException
{
int c=super.read();
return c==-1?c:Character.toUpperCase((char)c);
}

public int read(byte[] b,int offset,int len) throws IOException
{
int result=super.read(b, offset, len);
for (int i = 0; i < result; i++)
{
b[i]=(byte)Character.toUpperCase((char)b[i]);
}
return result;
}
}
并测试之
package myjavaIO;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;

public class InputTest
{
public static void main(String[] args)
{
int c;
InputStream inputStream;
try
{
inputStream = new UpperCaseInputStream(new BufferedInputStream(
new FileInputStream("test.txt")));
while((c=inputStream.read())>=0)
{
System.out.print((char)c);
}
}
catch (Exception e)
{
e.printStackTrace();
}

}
}

源码链接：

http://download.csdn.net/detail/kaikai_sk/9871802