Observer Programming Example

最新推荐文章于 2019-05-16 16:05:56 发布

最新推荐文章于 2019-05-16 16:05:56 发布 · 105 阅读

文章标签：

#Java

本文介绍了一个简单的Java观察者模式实现案例。该案例通过`SimpleSubject`类和`SimpleObserver`类展示了如何在状态改变时通知观察者。`SimpleSubject`继承自`java.util.Observable`，并实现了状态更新与观察者的通知逻辑。

Subject:

import java.util.Observable;

public class SimpleSubject extends Observable{
private SimpleObserver observer = null;

private String state = null;

SimpleSubject(){
  observer = new SimpleObserver();
  this.addObserver(observer);

  System.out.println("Subject initialed ok");
}

public String getState(){
  return state;
}

public void setState(String s){
  this.state = s;
  this.setChanged();
  this.notifyObservers();
}
}

Observer:

import java.util.Observable;
public class SimpleObserver implements java.util.Observer{
  public void update(Observable o, Object arg){
   System.out.println("Subject changed....");
  }
}

main:
public class Test {
public static void main(String[] args) {
  SimpleSubject ss = new SimpleSubject();

  ss.setState("new state get");
}
}

Notion: Don't forget to use setChanged when some fields changes, and use notifyObservers when some events happen.