watcher.java

来自「java与模式 一书的源码」· Java 代码 · 共 18 行

package com.javapatterns.observer.watching;

import java.util.Observable;
import java.util.Observer;

public class Watcher implements Observer
{
	public Watcher(Watched w)
    {
        w.addObserver(this);
    }

    public void update( Observable ob, Object arg)
    {
        System.out.println("Data has been changed to:  '" + ((Watched)ob).retrieveData() + "'");
    }
}