mysql-下面的Java代码有问题吗

<code>/** *  */private static final long serialVersionUID = 1L;private JPanel contentPane;private JTextField text_confirm;private JTextField text_usr;private JTextField text_pwd;private JButton btn_save,btn_cancel;private JLabel user,passwd,confirm;private Connection conn;private Statement statement;/** * Launch the application. */public static void main(String[] args) {    EventQueue.invokeLater(new Runnable() {        public void run() {            try {                Regist frame = new Regist();                frame.setVisible(true);            } catch (Exception e) {                e.printStackTrace();            }        }    });}/** * Create the frame. */public Regist() {    super("注册新用户");    this.setDefaultCloseOperation(EXIT_ON_CLOSE);    this.setVisible(true);    setBounds(100, 100, 450, 300);    contentPane = new JPanel();    contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));    setContentPane(contentPane);    contentPane.setLayout(null);    user = new JLabel("用  户  名");    user.setBounds(57, 36, 54, 15);    contentPane.add(user);    passwd = new JLabel("密       码");    passwd.setBounds(57, 76, 54, 15);    contentPane.add(passwd);    confirm = new JLabel("确认密码");    confirm.setBounds(57, 121, 54, 15);    contentPane.add(confirm);    text_usr = new JTextField();    text_usr.setBounds(141, 33, 155, 21);    contentPane.add(text_usr);    text_usr.setColumns(10);    text_pwd = new JTextField();    text_pwd.setBounds(141, 73, 155, 21);    contentPane.add(text_pwd);    text_pwd.setColumns(10);    text_confirm = new JTextField();    text_confirm.setBounds(141, 118, 155, 21);    contentPane.add(text_confirm);    text_confirm.setColumns(10);    btn_save = new JButton("确定");    btn_save.setBounds(79, 171, 93, 23);    contentPane.add(btn_save);    this.btn_save.addActionListener(this);    btn_cancel = new JButton("取消");    btn_cancel.setBounds(256, 171, 93, 23);    contentPane.add(btn_cancel);    this.btn_cancel.addActionListener(this);}public Connection getConnection() throws SQLException {    try {        Class.forName("com.mysql.jdbc.Driver");    } catch (ClassNotFoundException e) {        e.printStackTrace();    }    Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/sign","root","514519");    return conn;}@Overridepublic void actionPerformed(ActionEvent e) {    if(e.getSource()==btn_save){        if(text_usr.getText().isEmpty()&&text_pwd.getText().isEmpty())            JOptionPane.showMessageDialog(this, "请填写用户名和密码");        String sql="insert into signs values ('"+text_usr.getText()+","+text_pwd.getText()+"')";        try {               conn=getConnection();        } catch (SQLException e1) {            e1.printStackTrace();        }        try {            statement=conn.createStatement();        } catch (SQLException e1) {            e1.printStackTrace();        }        try {            statement.executeUpdate(sql);        } catch (SQLException e1) {            e1.printStackTrace();        }        try {            statement.close();        } catch (SQLException e2) {            e2.printStackTrace();        }        try {            conn.close();        } catch (SQLException e1) {            e1.printStackTrace();        }    }       if(e.getSource()==btn_cancel){    }}</code>