读书笔记—head first 设计模式— 观察者模式

import java.util.ArrayList;
interface Show{
	void show(String text);
}
interface Observer{
	void update(String text);
}
interface Observable{
	void registerObserver(Observer o);
	void removeObserver(Observer o);
	void notifyObservers();
}
class Myclass implements Observable{
	ArrayList<Observer> students;
	public Myclass() {
		// TODO Auto-generated constructor stub
		students = new ArrayList<>();
	}
	@Override
	public void registerObserver(Observer o) {
		// TODO Auto-generated method stub
		this.students.add(o);
	}
	@Override
	public void removeObserver(Observer o) {
		// TODO Auto-generated method stub
		int i = students.indexOf(o);
		if(i >= 0)
			students.remove(i);
	}
	@Override
	public void notifyObservers() {
		// TODO Auto-generated method stub
		for (int i = 0; i < students.size(); i++) {
			students.get(i).update(String.valueOf(i+1));
		}
	}
	
}
class Me implements Observer,Show {
	Observable myObservable;
	Me(Observable o){
		myObservable = o;
		myObservable.registerObserver(this);
	}
	@Override
	public void update(String text) {
		// TODO Auto-generated method stub
		show(text);
	}
	@Override
	public void show(String text) {
		// TODO Auto-generated method stub
		System.out.println("我是第"+text+"个");
	}
	
}
public class Observers {
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Observable myClass = new Myclass();
		Observer me = new Me(myClass);
		myClass.notifyObservers();
	}
}