package Pak;

public interface Sourceable {
    public void method();
}

 1 package Pak;
 2 
 3 public class Source implements     Sourceable {
 4     
 5     @Override
 6     public void method(){
 7         System.out.println("the original method!");
 8         
 9     }
10 }

 1 package Pak;
 2 
 3 public class Proxy implements Sourceable {
 4     private Source source;
 5 
 6     public Proxy() {
 7         super();
 8         this.source = new Source();
 9     }
10 
11     @Override
12     public void method() {
13         // TODO Auto-generated method stub
14         before();
15         source.method();
16         after();
17     }
18 
19     private void after() {
20         System.out.println("after proxy!");
21     }
22 
23     private void before() {
24         System.out.println("Before proxy!");
25     }
26 }

 1 package Pak;
 2 
 3 import java.util.ArrayList;
 4 import java.util.List;
 5 
 6 public class Main {
 7 
 8     public static void main(String[] args) throws Exception {
 9         Sourceable source = new Proxy();
10         source.method();
11 
12     }
13 }