Decorator Pattern

2008-03-26 16:39:00

　标签：装饰模式　　　[推送到技术圈]

一、装饰者模式：运行时动态地将责任附加到对象上。

1、装饰者与被装饰对象有相同的超类型

2、一个或多个装饰者包装一个对象

3、装饰者在所委托被装饰者的行为之前与/或之后加上自己的行为

4、可在运行时动态地不限量地装饰

二、装饰者缺点：大量小类、增加实例化难度

三、java.io中装饰者应用

四、示例：

1、设计UML图

2、Coding

1>.抽象组件类

//Component:abstract class
public abstract class Beverage{

    String description = "Unknown Beverage";

    public String getDescription(){
         return description;
    }

    public abstract double cost();

}

2>.具体组件类

//具体组件类:Espresso
public class Espresso extends Beverage{

    public Espresso(){
         description = "Espresso";
    }

    public double cost(){
         return 1.99;
    }

}

//具体组件类:HouseBlend
public class HouseBlend extends Beverage{

    public HouseBlend(){
         description = "HouseBlend";
    }

    public double cost(){
         return .89;
    }

}

//具体组件类:DarkRoast
public class DarkRoast extends Beverage{

    public DarkRoast(){
         description = "DarkRoast";
    }

    public double cost(){
         return 2.59;
    }

}

//具体组件类:Decaf
public class Decaf extends Beverage{

    public Decaf(){
         description = "Decaf";
    }

    public double cost(){
         return 4.00;
    }

}

3>.装饰者

//装饰者：抽象类CondimentDecorator
public abstract class CondimentDecorator extends Beverage{

public abstract String getDescription();

}

//装饰者：Milk
public class Milk extends CondimentDecorator{

    Beverage beverage;

    public Milk(Beverage beverage){
         this.beverage = beverage;
    }

    public String getDescription(){
         return beverage.getDescription() + ",Milk";
    }

    public double cost(){
         return .55 + beverage.cost();
    }

}

//装饰者：Mocha
public class Mocha extends CondimentDecorator{

    Beverage beverage;

    public Mocha(Beverage beverage){
         this.beverage = beverage;
    }

    public String getDescription(){
         return beverage.getDescription() + ",Mocha";
    }

    public double cost(){
         return .20 + beverage.cost();
    }

}

//装饰者：Soy
public class Soy extends CondimentDecorator{

    Beverage beverage;

    public Soy(Beverage beverage){
         this.beverage = beverage;
    }

    public String getDescription(){
         return beverage.getDescription() + ",Soy";
    }

    public double cost(){
         return 1.56 + beverage.cost();
    }

}

//装饰者：Whip
public class Whip extends CondimentDecorator{

    Beverage beverage;

    public Whip(Beverage beverage){
         this.beverage = beverage;
    }

    public String getDescription(){
         return beverage.getDescription() + ",Whip";
    }

    public double cost(){
         return .99 + beverage.cost();
    }

}

4>.测试

//Test class
public class TestD{

    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());

         Beverage beverage3 = new HouseBlend();
         beverage3 = new Soy(beverage3);
         beverage3 = new Mocha(beverage3);
         beverage3 = new Whip(beverage3);
         System.out.println(beverage3.getDescription() + "$" + beverage3.cost());

    }

}

5>.测试结果

五、java.io装饰者：大写转小写

1、java.io.FilterInputStream装饰者

//java.io Decorator：change UpperCase to LowerCase
import java.io.FilterInputStream;
import java.io.InputStream;
import java.io.IOException;
import java.lang.Character;

public class LowerCaseInputStream extends FilterInputStream{

    public LowerCaseInputStream(InputStream is){
         super(is);
    }

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

    public int read(byte[] b, int offset, int len) throws IOException{
         int c = super.read(b,offset,len);
         for(int i = offset; i < offset + c; i++){
              b[i] = (byte)Character.toLowerCase((char)b[i]);
         }
         return c;
    }
}

2、资源testl.txt

//testl.txt
import java.io.InputStream;
import java.lang.String;
import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;

public class TestL{

    public static void main(String[] arg) throws IOException{
         int c;
         InputStream is = new LowerCaseInputStream(new BufferedInputStream(new FileInputStream("testl.txt")));
         while((c = is.read()) >= 0){
              System.out.print((char)c);
         }
         is.close();
    }

}

3、测试类

//Test class
import java.io.InputStream;
import java.lang.String;
import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;

public class TestL{

    public static void main(String[] arg) throws IOException{
         int c;
         InputStream is = new LowerCaseInputStream(new BufferedInputStream(new FileInputStream("testl.txt")));
         while((c = is.read()) >= 0){
              System.out.print((char)c);
         }
         is.close();
    }

}

4、测试结果

本文出自 “不服不行” 博客，转载请与作者联系！

上一篇 20080326　　下一篇 Head First Java Note

类别：Design Pattern ┆ 技术圈() ┆ 阅读() ┆ 评论() ┆推送到技术圈 ┆返回首页

相关文章

文章评论

昵称：
验证码：		点击图片可刷新验证码　　博客过2级，无需填写验证码
内容：