package test.edu.mainrole; 
 
import java.util.ArrayList; 
 
public abstract class AbsRole { 
 
  private ArrayList<IObserver> list = new ArrayList<IObserver>(); 
 
  public void add(IObserver observer) { 
    list.add(observer); 
 
  } 
 
  public void delete(IObserver observer) { 
    list.remove(observer); 
  } 
 
  public void nodifyObservers(String newState) { 
    for (IObserver observer : list) { 
      observer.update(newState); 
    } 
  } 
} 

package test.edu.mainrole; 
 
public class Role extends AbsRole { 
 
  private String state; 
 
  public String getState() { 
    return state; 
  } 
 
  public void change(String nupdate) { 
    state = nupdate; 
    this.nodifyObservers(state); 
  } 
} 

package test.edu.mainrole; 
 
public interface IObserver { 
  public void update(String newState); 
     
} 

package test.edu.mainrole; 
 
public class ObserverObj1 implements IObserver{ 
 
  private String observerState; 
 
  @Override 
  public void update(String state) { 
    observerState = state; 
    System.out.println("观察者1的状态为：" + observerState); 
  } 
 
} 

package test.edu.mainrole; 
 
public class ObserverObj2 implements IObserver { 
   
  private String observerState; 
 
  @Override 
  public void update(String state) { 
    observerState = state; 
    System.out.println("观察者2的状态为：" + observerState); 
  } 
} 

package test.edu.mainrole; 
 
public class Client { 
 
  /** 
   * @param args 
   */ 
  public static void main(String[] args) { 
 
    Role subject = new Role(); 
    IObserver observer1 = new ObserverObj1(); 
    IObserver observer2 = new ObserverObj2(); 
    subject.add(observer1); 
    subject.add(observer2); 
    subject.change("update!"); 
  } 
} 

观察者1的状态为：update!

观察者2的状态为：update!