窗体监听事件WindowListener

EXIT_ON_CLOSE：结束窗口所在的应用程序。在窗口被关闭的时候会退出JVM。

DISPOSE_ON_CLOSE：隐藏当前窗口，并释放此窗体占有的资源。如果程序没有其他线程在运行，当所有窗口都被dispose后，JVM也会退出。

举例说明：关闭窗体A，窗体B也会退出。关闭窗体B，窗体A不会退出。

public class Demo{
    public static void main(String[] args){
        JFrame window1=new JFrame("窗体A");
        JFrame window2=new JFrame("窗体B");
        window1.setBounds(100,100,200,100);
        window2.setBounds(400,100,200,100);
        window1.setVisible(true);
        window2.setVisible(true);
        window1.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        window2.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
    }
}

【窗体监听事件 WindowListener】
windowOpened      打开
windowActivated   激活（获得焦点状态）
windowDeactivated 非激活（失去焦点状态）
windowIconified   最小化
windowDeiconified 最小化恢复正常
windowClosing     关闭（右上角X），优先于windowClosed
windowClosed      关闭，DISPOSE_ON_CLOSE时才会被调用

public class Demo extends JFrame {
    public Demo() {
        setBounds(100, 100, 300, 300);
        setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
        setVisible(true);
        addWindowListener(new MyWindowListener());//调用方法类对象
    }

    class MyWindowListener implements WindowListener {
        public void windowOpened(WindowEvent e) {
            System.out.println("窗体打开");
        }

        public void windowClosing(WindowEvent e) {
            System.out.println("窗体关闭exit");
        }

        public void windowClosed(WindowEvent e) {
            System.out.println("窗体关闭dispose");
        }

        public void windowIconified(WindowEvent e) {
            System.out.println("窗体最小化");
        }

        public void windowDeiconified(WindowEvent e) {
            System.out.println("窗体最小化恢复正常");
        }

        public void windowActivated(WindowEvent e) {
            System.out.println("窗体激活");
        }
        
        public void windowDeactivated(WindowEvent e) {
            System.out.println("窗体非激活");
        }
    }

    public static void main(String[] args) {
        new Demo();
    }
}