JavaSE 窗口事件类（WindowEvent）实现

{相关信息}
窗口事件(WindowEvent)指窗口状态改变的事件,例如当窗口 Window 对象的打开、关闭、激活、停用或者焦点转移到窗口内,
以及焦点移除而生成的事件，一般发生在 Window、Frame、Dialog 等类的对象上。使用窗口事件必须为组件添加一个实现 WindowListener 接口的事件处理器,该接口包含以下 7 种方法：
void windowActivated(WindowEvent e):窗口被激活时发生
void windowClosed(WindowEvent e):窗口关闭之后发生
void windowClosing(WindowEvent e):窗口关闭过程中发生
void windowDeactivated(WindowEvent e):窗口不再处于激活状态时发生
void windowDeiconified(WindowEvent e):窗口大小从最小到正常时发生
void windowIconified(WindowEvent e):窗口从正常到最小时发生
void windowOpened(WindowEvent e):窗口第一次被打开时发生

{相关代码}

package sup.orange.learn;

import java.awt.*;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;

/**
 * Created by re-x on 11/2/14.
 */
public class WindowEventDemo extends Frame {

    String string = null;

    public WindowEventDemo () {
        super();
        init();
    }

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

    public void init() {
        addWindowListener(new WindowListener() {
            @Override
            public void windowOpened(WindowEvent e) {
                string = "window opened";
                System.out.println(string);
                repaint();
            }

            @Override
            public void windowClosing(WindowEvent e) {
                string = "window closing";
                System.out.println(string);
                setVisible(false);
                dispose();
                System.exit(0);
            }

            @Override
            public void windowClosed(WindowEvent e) {
                string = "window closed";
                System.out.println(string);
                repaint();
            }

            @Override
            public void windowIconified(WindowEvent e) {
                string = "window iconified";
                System.out.println(string);
                repaint();
            }

            @Override
            public void windowDeiconified(WindowEvent e) {
                string = "window deiconified";
                System.out.println(string);
                repaint();
            }

            @Override
            public void windowActivated(WindowEvent e) {
                string = "window activated";
                System.out.println(string);
                repaint();
            }

            @Override
            public void windowDeactivated(WindowEvent e) {
                string = "window deactivated";
                System.out.println(string);
                repaint();
            }
        });

        setSize(200, 200);
        setVisible(true);

    }

    public void paint(Graphics g) {
        g.drawString(string, 30, 100);
    }
}