1类图

设计模式之观察者模式_java

 

2java示例


public class Test {

  public static void main(String[] args) {
    Plane plane=new Plane("J20 a001");
    Observer observer=new Radar();
    plane.addObserver(observer);
    plane.setDistance(9000);
    
  }

}
public class Plane extends Observable {
  private String name;
  public Plane(String name){
    this.name=name;
  }
  
  
  public String getName() {
    return name;
  }


  public void setDistance(int distance){
    if(distance<10000){
      this.setChanged();
      this.notifyObservers();
    }
  }
}



public class Radar implements Observer {

  @Override
  public void update(Observable o, Object arg) {
    Plane plane=(Plane)o;
    System.out.println(plane.getName()+" has been discovered");
  }

}