Java设计模式中的观察者模式

//抽象观察者
public interface Observer {
    void action();
}
//抽象主题
abstract class Subject{
    protected List<Observer> observers = new ArrayList<>();
    public void addObserver(Observer observer) {
        observers.add(observer);
    }
    public void removeObserver(Observer observer) {
        observers.remove(observer);
    }
    public abstract void notifyObserver();
}
//具体主题-被观察者
class Baby extends Subject{
    @Override
    public void notifyObserver() {
        System.out.println("baby cry");
        observers.forEach(Observer::action);
    }
}
//具体观察者
class Dad implements Observer {
    @Override
    public void action() {
        System.out.println("dad feed baby");
    }
}
//具体观察者
class Mum implements Observer {
    @Override
    public void action() {
        System.out.println("mum hug baby");
    }
}

public class Client {
    public static void main(String[] args) {
        Baby baby = new Baby();
        baby.addObserver(new Mum());
        baby.addObserver(new Dad());
        baby.notifyObserver();
    }
}

//抽象观察者
public interface Observer {
    void action(Event event);
}
//抽象主题
abstract class Subject {
    protected List<Observer> observers = new ArrayList<>();
    public void addObserver(Observer observer) {
        observers.add(observer);
    }
    public void removeObserver(Observer observer) {
        observers.remove(observer);
    }
    public abstract void notifyObserver();
}
//具体主题-被观察者
class Baby extends Subject {
    @Override
    public void notifyObserver() {
        System.out.println("baby cry");
        CryEvent cryEvent = new CryEvent(new Date().getTime(), this);
        observers.forEach(observer -> observer.action(cryEvent));
    }
}
//抽象事件
abstract class Event {
    public abstract Object getSource();
}
//具体事件
class CryEvent extends Event {
    public long when;
    Baby source;
    public CryEvent(long when, Baby source) {
        this.when = when;
        this.source = source;
    }
    @Override
    public Baby getSource() {
        return source;
    }
}
//具体观察者
class Dad implements Observer {
    @Override
    public void action(Event event) {
        System.out.println("dad feed baby");
        if(event.getSource() instanceof Baby){
            System.out.println("dad对事件源进行处理");
        }
    }
}
//具体观察者
class Mum implements Observer {
    @Override
    public void action(Event event) {
        System.out.println("mum hug baby");
        if(event.getSource() instanceof Baby){
            System.out.println("mum对事件源进行处理");
        }
    }
}

public class Client {
    public static void main(String[] args) {
       Baby baby = new Baby();
       baby.addObserver(new Dad());
       baby.addObserver(new Mum());
       baby.notifyObserver();
    }
}

public class MainFrame extends JFrame {
    public MainFrame() throws HeadlessException {
        //定义一个具体主题
        Button button = new Button("click");
        //给主题添加观察者(鼠标监听)
        button.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseClicked(MouseEvent e) {
                //MouseEvent就是具体事件
                System.out.println("按钮被点击");
            }
        });
        //给主题添加观察者(键盘监听)
        button.addKeyListener(new KeyAdapter() {
            @Override
            public void keyTyped(KeyEvent e) {
                //KeyEvent就是具体事件
                System.out.println("按下" + e.geTKEyChar());
            }
        });
        add(button);
        setSize(100,100);
        this.setLocationRelativeTo(null);
        this.setVisible(true);
    }
    public static void main(String[] args) {
        new MainFrame();
    }
}