package checkbox;import java.awt.*;import java.awt.event.*;import java.applet.*;import javax.swing.*;public class update extends Applet {  boolean isStandalone = false;  JCheckBox jCheckBox1 = new JCheckBox();  JCheckBox jCheckBox2 = new JCheckBox();  JCheckBox jCheckBox3 = new JCheckBox();  /**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*/  public update() {  }  /**Initialize the applet*/  public void init() {    try {      jbInit();    }    catch(Exception e) {      e.printStackTrace();    }  }  /**Component initialization*/  private void jbInit() throws Exception {    jCheckBox1.setText("圓形");    jCheckBox1.addActionListener(new java.awt.event.ActionListener() {      public void actionPerformed(ActionEvent e) {        jCheckBox1_actionPerformed(e);      }    });    jCheckBox2.setText("正方形");    jCheckBox2.addActionListener(new java.awt.event.ActionListener() {      public void actionPerformed(ActionEvent e) {        jCheckBox2_actionPerformed(e);      }    });    jCheckBox3.setText("扇形");    jCheckBox3.addActionListener(new java.awt.event.ActionListener() {      public void actionPerformed(ActionEvent e) {        jCheckBox3_actionPerformed(e);      }    });    this.add(jCheckBox1, null);    this.add(jCheckBox2, null);    this.add(jCheckBox3, null);  }  /**Get Applet information*/  public String getAppletInfo() {    return "Applet Information";  }  /**Get parameter info*/  public String[][] getParameterInfo() {    return null;  }  void jCheckBox1_actionPerformed(ActionEvent e) {   repaint();  }  public void paint(Graphics g){    g.clearRect(0,20,300,280);    if(jCheckBox1.isSelected())          g.drawOval(60,60,30,30);    if(jCheckBox2.isSelected())          g.drawRect(120,60,30,30);    if(jCheckBox3.isSelected())          g.drawArc(180,60,30,30,0,130);  }  void jCheckBox3_actionPerformed(ActionEvent e) {    repaint();  }  void jCheckBox2_actionPerformed(ActionEvent e) {     repaint();  }  public void update(Graphics g){     paint(g);  }}