观察者模式

/**
 * 抽象观察者接口
 * Created by sky-mxc on 2016/12/25.
 */
public interface IObserver {
 
    /**
     * 主题发生变化
     * @param str
     */
    void update(String str);
}

		/**
 * 抽象主题
 * Created by sky-mxc on 2016/12/25.
 */
public abstract class ISubject {
 
    //观察者 集合
    protected List<IObserver> observers = new ArrayList<>();
 
    //主题名字
    protected String name;
 
    public ISubject(String name) {
        this.name = name;
    }
 
    /**
     * 增加 观察者
     * @param observer 观察者
     */
   public  void addObserver(IObserver observer){
       observers.add(observer);
   }
 
    /**
     * 移除观察者
     * @param observer 观察者
     */
   public void removeObserver(IObserver observer){
       observers.remove(observer);
   }
 
    /**
     * 通知观察者
     * @param str 通知内容
     */
   protected abstract void notifyUpdate(String str);
}

/**
 * 具体主题
 * Created by sky-mxc on 2016/12/25.
 */
public class Subject extends ISubject {
 
    public Subject(String name) {
        super(name);
    }
 
    @Override
    public void notifyUpdate(String str) {
        for (IObserver observer :observers){
            observer.update(str+"\t\t\t--- "+name);
        }
    }
}

/**
 * 具体观察者
 * Created by sky-mxc on 2016/12/25.
 */
public class Observer implements IObserver {
    private String name;
 
    public Observer(String name) {
        this.name = name;
    }
 
    @Override
    public void update(String str) {
        System.out.println(name+"接收到了通知："+str);
    }
}

public class Main {

    public static void main(String[] args) {
        Observer observer1 =new Observer("张三");
        Observer observer2 =new Observer("李四");
        Observer observer3 =new Observer("王五");

        Subject subject = new Subject("PM");
        subject.addObserver(observer1);
        subject.addObserver(observer2);
        subject.addObserver(observer3);
        for (int i=0;i<5;i++){
            subject.notifyUpdate("通知："+System.currentTimeMillis());
            try {
                Thread.sleep(1000*3);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("\n");
        }
    }
}