装饰者模式

小灰灰 2022-07-13 02:58 109阅读 0赞

《Head First Design Patterns》装饰者模式学习练习：

装饰者模式我们常见的Demo：文件读写io时候，会有InputStream,FileInputStreat,BufferedInputStream的使用。常见的

FileInputStream fileInputStream=**new** FileInputStream(string);

BufferedInputSream bufferedInputStream=**new** BufferedInputStream(fileInputStream);

装饰者模式定义：动态地将责任附加到对象上，若要扩展功能，修饰者提供了比继承更有弹性的替代方案。

新增设计原则：

类应对扩展开放，对修改关闭（即 开放-关闭原则）

以选蛋糕为例，可能会有草莓味，巧克力味，或者巧克力草莓味的，那么定义蛋糕的时候就需用到装饰者模式，以方便后期添加其他口味。

蛋糕抽象类：

public abstract class Cake {
    	protected String description = "Cake";
    	public String getDescrip(){
    		return description;
    	}
    }

甜味蛋糕具体类：

public class SweetCake extends Cake{
    	public SweetCake(){
    		description = "sweet cake";
    	}
    }

蛋糕修饰类：

public abstract class CakeDecorater extends Cake{
    	public abstract String getDescrip();
    }

草莓蛋糕：

public class Strawberry extends CakeDecorater{
    	private Cake cake;
    	public Strawberry(Cake cake){
    		this.cake = cake;
    	}
    	@Override
    	public String getDescrip() {
    		// TODO Auto-generated method stub
    		return " strawberry " + cake.getDescrip();
    	}
    	public String getTaste(){
    		return "strawberry";
    	}
    }

巧克力蛋糕：

public class Chocolate extends CakeDecorater{
    	private Cake cake;
    	public Chocolate(Cake cake){
    		this.cake = cake;
    	}
    	@Override
    	public String getDescrip() {
    		// TODO Auto-generated method stub
    		return " chocalate " + cake.getDescrip();
    	}
    	public String getTaste(){
    		return "chocalate";
    	}
    }

测试类：

public class TestDecorater {
    	public static void main(String[] args){ 
    		Cake cake = new SweetCake();
    		Cake choCake = new Chocolate(cake);
    		System.out.println(choCake.getDescrip());
    		Cake strawCake = new Strawberry(choCake);
    		System.out.println(strawCake.getDescrip());
    	}
    }

测试结果：

![Image 1][]

![Center][]

[Image 1]: 
[Center]: /images/20220713/c2f159f1385e43d09fddf71f2eff8ede.png