你可以定义一个监听器界面：

You can define a Listener interface:

public interface EventListener {
    void fireEvent (Event e);
}

然后在你的代码中：

EventListener lst = new EventListener() {
    @Override
    public void fireEvent (Event e) {
        //do what you want with e
    }
}

someObject.setListener(lst);
someObject.somethingHappened();

然后在someObject中（实际上你可能会有一个监听器列表）：

Then in someObject (in practice you would probably hold a list of listeners):

public class SomeObject {
    private EventListener lst;

    public void setListener (EventListener lst) {
        this.lst = lst;
    }

    public void somethingHappened () {
        lst.fireEvent(new Event("Something Happened"));
    }
}