//事件监听机制    import java.awt.*;  import java.awt.event.*;    public class TestEvent {      public static void main(String[] args) {          Frame f = new Frame("Test");          Button b = new Button("Press Me!");            Monitor bh = new Monitor(); //实现了某种监听器接口的类的对象            b.addActionListener(bh);    //注册            f.add(b, BorderLayout.CENTER);          f.pack();          f.setVisible(true);      }  }    //实现了某种监听器接口的类 class Monitor implements ActionListener {      public void actionPerformed(ActionEvent e) {          System.out.println("A button has been pressed");      }  }  [java] import java.awt.*;  import java.awt.event.*;   public class TestActionEvent {      public static void main(String[] args) {          Frame f = new Frame("Test");          Button b1 = new Button("Start");          Button b2 = new Button("Stop");            //一个监听器类被两个button监听          Monitor2 bh = new Monitor2();          b1.addActionListener(bh);          b2.addActionListener(bh);            b2.setActionCommand("Game over");            f.add(b1,"North");          f.add(b2,"Center");          f.pack();            f.setVisible(true);        }    }    class Monitor2 implements ActionListener {      public void actionPerformed (ActionEvent e) {          System.out.println("A button has been pressed," +              "the relative info is:\n" + e.getActionCommand());      }  }  

package com.javaedu.event;import java.util.EventObject;/** * 事件类,用于封装事件源及一些与事件相关的参数. * @author Eric */public class CusEvent extends EventObject {    private static final long serialVersionUID = 1L;    private Object source;//事件源        public CusEvent(Object source){        super(source);        this.source = source;    }    public Object getSource() {        return source;    }    public void setSource(Object source) {        this.source = source;    }}

package com.javaedu.event;import java.util.EventListener;/** * 事件监听器，实现java.util.EventListener接口。定义回调方法，将你想要做的事 * 放到这个方法下,因为事件源发生相应的事件时会调用这个方法。 * @author Eric */public class CusEventListener implements EventListener {        //事件发生后的回调方法    public void fireCusEvent(CusEvent e){        EventSourceObjecteObject = (EventSourceObject)e.getSource();        System.out.println("My name has been changed!");        System.out.println("I got a new name,named \""+eObject.getName()+"\"");    }}

package com.javaedu.event;import java.util.HashSet;import java.util.Iterator;import java.util.Set;/** * 事件源. * @author Eric */public class EventSourceObject {    private String name;    //监听器容器    private Set<CusEventListener> listener;    public EventSourceObject(){        this.listener = new HashSet<CusEventListener>();        this.name = "defaultname";    }    //给事件源注册监听器    public void addCusListener(CusEventListener cel){        this.listener.add(cel);    }    //当事件发生时,通知注册在该事件源上的所有监听器做出相应的反应（调用回调方法）    protected void notifies(){        CusEventListener cel = null;        Iterator<CusEventListener> iterator = this.listener.iterator();        while(iterator.hasNext()){            cel = iterator.next();            cel.fireCusEvent(new CusEvent(this));        }    }    public String getName() {        return name;    }    //模拟事件触发器，当成员变量name的值发生变化时，触发事件。    public void setName(String name) {        if(!this.name.equals(name)){            this.name = name;            notifies();        }          }}

package com.javaedu.event;public class MainTest {    /**     * @param args     */    public static void main(String[] args) {        EventSourceObject object = new EventSourceObject();        //注册监听器        object.addCusListener(new CusEventListener(){            @Override            public void fireCusEvent(CusEvent e) {                super.fireCusEvent(e);            }        });        //触发事件        object.setName("eric");    }}