为什么两个按钮不起作用，求大神指教

public class User extends Frame implements ActionListener{
Label name=new Label("用户名：");//创建标签
Label paseword=new Label("密 码：");//创建标签
TextField nameTextField=new TextField(10);//单行文本域，输入用户名
TextField pasewordTextField=new TextField(10);//单行文本域，输入密码
Button submit=new Button("提交");//提交按钮
Button reset=new Button("重置");//重置按钮
User(){
pasewordTextField.setEchoChar('*');//密码加密
//三个面板，用于存放以上六个组件
Panel panel1=new Panel();
Panel panel2=new Panel();
Panel panel3=new Panel();
//将组件添加到相应的面板中
panel1.add(name);
panel1.add(nameTextField);

     panel2.add(paseword);
     panel2.add(pasewordTextField);

     panel3.add(submit);
     panel3.add(reset);
     //对单行文本框和按钮添加事件监听器
     nameTextField.addActionListener(this);
     pasewordTextField.addActionListener(this);
     submit.addActionListener(this);
     reset.addActionListener(this);
     //将面板添加到窗口中
     add(panel1,"North");
     add(panel2,"Center");
     add(panel3,"South");

 }
public void actionPerformed(ActionEvent e) {
    if(e.getSource() instanceof TextField){//判断触发事件的是不是TextField
        Object object=e.getSource();
        if(object==nameTextField){
            pasewordTextField.requestFocus();}
        if(object==pasewordTextField){
            nameTextField.requestFocus();}
    } 
    if(e.getSource() instanceof Button){//判断触发事件的是不是Button  
        if(e.getActionCommand().equals("提交")){
            nameTextField.setText(null);           
            pasewordTextField.setText(null);}
        if(e.getActionCommand().equals("重置")){
            nameTextField.setText(null);
            pasewordTextField.setText(null);}
    }
}
public static void main(String[] args) {
    final User user=new User();
    user.setVisible(true);
    user.setSize(250,200);
    user.addWindowListener(new WindowAdapter(){//窗口关闭
        public void windowClosing(WindowEvent e){
            user.dispose();
        }
    });
}

}

按钮起作用了，你可以在按钮里面加System.out.print()输出有数据，应该是是你的nameTextField.setText(null);使用有误，我使用nameTextField.setText("任意字符"); 可以看到会改变

我看下下它的源码，当你设置的内容为null或者为空时，不会更新，即如果你传递的字符串为null或者""，不会更新，所以如果你要擦除，可以传递" "(注意中间有个空格)
，代码解释如下：
TextField.setText(String t)源码：

     public void setText(String t) {
        super.setText(t);

        // This could change the preferred size of the Component.
        invalidateIfValid();
    }

它的父类TextComponent的setText(String t)代码如下：

     /**
     * Sets the text that is presented by this
     * text component to be the specified text.
     * @param       t   the new text;
     *                  if this parameter is <code>null</code> then
     *                  the text is set to the empty string ""
     * @see         java.awt.TextComponent#getText
     */
    public synchronized void setText(String t) {
        boolean skipTextEvent = (text == null || text.isEmpty())
                && (t == null || t.isEmpty());
        text = (t != null) ? t : "";
        TextComponentPeer peer = (TextComponentPeer)this.peer;
**        // Please note that we do not want to post an event
****        // if TextArea.setText() or TextField.setText() replaces an empty text****
**        // by an empty text, that is, if component's text remains unchanged.****
        if (peer != null && !skipTextEvent) {
            peer.setText(text);
        }
    }

注意我加粗的部分