观察者模式

被观察对象、观察者

 

public interface Subject {

 void addListner(Listener listener);

 void removeListner(Listener listener);
 
 void advice();
 

}

 

public interface Listener {
 
 
 void update();

}

 

 

 

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class ConcreteSubject implements Subject {

 private List<Listener> list = new ArrayList<Listener>();

 public void addListner(Listener listener) {
  list.add(listener);

 }

 
 public void removeListner(Listener listener) {
  list.remove(listener);

 }
 public void advice() {
  Iterator<Listener> listIterator = list.iterator();
  while (listIterator.hasNext()) {
              Listener listener=listIterator.next();
              listener.update();
  }

 }

}