Help!刚写了个画图程序，运行出错！大家帮我看下出了什么问题
主程序：
import   java.awt.*;
import   java.awt.event.*;
import   java.applet.*;
import   javax.swing.*;

import   java.util.*;

/**
  *   <p> Title:   </p>
  *   <p> Description:   </p>
  *   <p> Copyright:   Copyright   (c)   2007 </p>
  *   <p> Company:   </p>
  *   @author   not   attributable
  *   @version   1.0
  */

public   class   WallFrame   extends   Applet   implements   ActionListener,MouseListener,MouseMotionListener{
    Point   start;
    Point   last;
    int   flag;
    int   i;
    private   Line   line1;
    private   rectangle   rectangle1;
    private   Graphics2D   g2D;
    private   boolean   isStandalone   =   false;
    JPanel   jPanel1   =   new   JPanel();
    JPanel   jPanel3   =   new   JPanel();
//new   GridLayout(6,0,5,5)
    JPanel   jPanel4   =   new   JPanel();
    BorderLayout   borderLayout2   =   new   BorderLayout();
    JButton   newfile   =   new   JButton( "新建 ");
    JButton   open   =   new   JButton( "打开 ");
    JButton   save   =   new   JButton( "保存 ");
    JButton   saveAs   =   new   JButton( "另存为 ");
    JButton   exit   =   new   JButton( "退出 ");
    JButton   line   =   new   JButton( "直线 ");
    JButton   rectangle   =   new   JButton( "矩形 ");
    JButton   color   =   new   JButton( "颜色 ");
    //GridBagLayout   gridBagLayout1   =   new   GridBagLayout();
    GridLayout   gridLayout1   =   new   GridLayout();
    JLabel   jLabel1   =   new   JLabel();
    JTextField   jTextField1   =   new   JTextField();
    JLabel   jLabel2   =   new   JLabel();
    FlowLayout   flowLayout1   =   new   FlowLayout();


    //Get   a   parameter   value
    public   String   getParameter(String   key,   String   def)   {
        return   isStandalone   ?   System.getProperty(key,   def)   :
            (getParameter(key)   !=   null   ?   getParameter(key)   :   def);
    }

    //Construct   the   applet


    //Initialize   the   applet
    public   void   init()   {
      //jPanel1   f=new   jPanel1( "paint ");
      //Container   f=jPanel1.getcont

      jPanel1.addMouseListener(new   WallFrame());
      jPanel1.addMouseMotionListener(new   WallFrame());
}

  public   void   paint(Graphics   g)   {