//定义接口
public interface Sourceable {  
2.    public void method();  
3.}  

//被装饰者实现接口
1.public class Source implements Sourceable {  
2.  
3.    @Override  
4.    public void method() {  
5.        System.out.println("the original method!");  
6.    }  
7.}  

//装饰者实现接口，并持有被装饰者的实例
1.public class Decorator implements Sourceable {  
2.  
3.    private Sourceable source;  
4.      
5.    public Decorator(Sourceable source){  
6.        super();  
7.        this.source = source;  
8.    }  
9.    @Override  
10.    public void method() {  
11.        System.out.println("before decorator!");  
12.        source.method();  
13.        System.out.println("after decorator!");  
14.    }  
15.}  

//测试类：
1.public class DecoratorTest {  
2.  
3.    public static void main(String[] args) {  
4.        Sourceable source = new Source();  
5.        Sourceable obj = new Decorator(source);  
6.        obj.method();  
7.    }  
8.}  

输出：

before decorator!
the original method!
after decorator!