import java.awt.event.WindowAdapter;
import java.awt.*;
import java.awt.event.WindowEvent;
import java.awt.event.*;
public class EventManagerDemo {
    public static void main(String args[]){
        final Frame f=new Frame("Test");
        Button b=new Button("Press ME");
        b.addActionListener(new ButtonHandler());
        f.setLayout(new FlowLayout());
        f.add(b);
        f.setSize(200,100);
        f.addWindowListener(new WindowAdapter(){
            public void WindowClosing(WindowEvent evt){
                f.setVisible(true);
                f.dispose();
                System.exit(0);

            }

        });
        f.setVisible(true);

    }

}
class ButtonHandler     implements ActionListener{
    
    public void actionPerformed(ActionEvent e){
        System.out.print("已经捕获");
    }
}

------解决方案--------------------
拼写错误

           public void WindowClosing(WindowEvent evt){

技巧：  
重写的方法加上 ＠Override