import java.awt.*;
import java.awt.event.*;

public class DrawLine extends Frame
{
    public DrawLine()
    {
        addWindowListener(new WindowAdapter()
        {
            public void windowClosing(WindowEvent e)
            {
                dispose();
                System.exit(0);
            }
        });
        this.addMouseListener(new MouseAdapter()
        {
            int orgX;
            int orgY;
            public void mousePressed(MouseEvent e)
            {
                orgX=e.getX();
                orgY=e.getY();
            }
            public void mouseReleased(MouseEvent e)
            {
                Graphics g=getGraphics();//为什么等号右边要这么写。
                g.setColor(Color.RED);
                g.setFont(new Font(null,Font.ITALIC|Font.BOLD,30));
                //g.setFont(Font.BOLD)为什么此处这么写会报错？为什么不能这么写？
                g.drawString(orgX+","+orgY,orgX,orgY);
                g.drawString(e.getX()+","+e.getY(),e.getX(),e.getY());
                g.drawLine(orgX,orgY,e.getX(),e.getY());
            }
        });
    }
    public static void main(String []args)
    {
        DrawLine dl=new DrawLine();
        dl.setSize(400,400);
        dl.setTitle("窗体");
        dl.setVisible(true);
    }
}