import java.awt.*;

 import javax.swing.*;

 class Gstudy extends JFrame{

     private int x1,y1,x2,y2;

     private newPanel panel=new newPanel();

     private JButton btn=new JButton("清除");

     public Gstudy()

     {

         setTitle("交互式绘图");

         setBounds(10,10,750,700);

         btn.addActionListener(new ClearList());

         panel.add(btn,BorderLayout.SOUTH);

         add(panel);

     }

     public static void main(String[] args)

     {

         Gstudy frm=new Gstudy();

         frm.setVisible(true);

         frm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

     }

     private class ClearList  implements ActionListener

     {

         @Override

         public void actionPerformed(ActionEvent e) {

             panel.paintComponent(panel.getGraphics());

         }

     }

     private class MyMouseList extends MouseAdapter

     {

         public void mousePressed(MouseEvent e)

         {

             x1=e.getX();

             y1=e.getY();

         }

     }

     private class MyMouseMotionList extends MouseMotionAdapter

     {

         public void mouseDragged(MouseEvent e)

         {

             x2=e.getX();

             y2=e.getY();

             Graphics g=panel.getGraphics();

             g.drawLine(x1, y1, x2, y2);

             x1=x2;

             y1=y2;

         }

     }

     private class newPanel extends JPanel

     {

         public newPanel()

         {

             this.addMouseMotionListener(new MyMouseMotionList());

             this.addMouseListener(new MyMouseList());

         }

         @Override

         protected void paintComponent(Graphics g) {

             // TODO Auto-generated method stub

             super.paintComponent(g);

         }

     }