程序有错 请

import java.awt.BorderLayout;import java.awt.Button;import java.awt.GridLayout;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.util.ArrayList;import java.util.List;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.JPanel;import javax.swing.JTextField;public class IdCard extends JFrame implements ActionListener {    JTextField jt1 = new JTextField(18);    JButton jb1 = new JButton("确定");    JPanel jp1 = new JPanel();    JPanel jp2 = new JPanel();    JLabel jl1 = new JLabel("身份证号码");    JLabel jl2 = new JLabel(" 第二代身份证号码：");    JLabel jl22 = new JLabel();    JLabel jl3 = new JLabel(" 所在省/直辖市：");    JLabel jl33 = new JLabel();    JLabel jl4 = new JLabel(" 所在市/直辖区：");    JLabel jl44 = new JLabel();    JLabel jl5 = new JLabel(" 所在县/区(旗)：");    JLabel jl55 = new JLabel();    JLabel jl6 = new JLabel(" 性别：");    JLabel jl66 = new JLabel();    JLabel jl7 = new JLabel(" 出生日期：");    JLabel jl77 = new JLabel();    public IdCard() {        super("身份证验证");        setLocation(500, 500);        jp1.add(jl1);        jp1.add(jt1);        jp1.add(jb1);        jb1.addActionListener(this);        jp2.add(jl2);        setVisible(false);        jp2.add(jl22);        jp2.add(jl3);        jp2.add(jl33);        jp2.add(jl4);        jp2.add(jl44);        jp2.add(jl5);        jp2.add(jl55);        jp2.add(jl6);        jp2.add(jl66);        jp2.add(jl7);        jp2.add(jl77);        add(jp1, BorderLayout.NORTH);        add(jp2);        jp2.setLayout(new GridLayout(6, 6, 5, 15));        pack();        setVisible(true);    }    public static void main(String[] args) {        new IdCard();    }    @Override    public void actionPerformed(ActionEvent e) {        if (jb1 == e.getSource()){            System.out.println("===========================");            String a = jt1.getText();            List<String> list = new ArrayList<String>();            list.add(a);            if (a == null || "".equals(a.trim())){                return;            } else {                if(!a.matches("\\d{17}[0-9X]")){                    jl22.setText("身份证有误，请重新输入");                    return;                }                jl22.setText(a);            }            int d=Integer.parseInt(String.valueOf(list.get(0).charAt(16)));            if (d == 1) {                jl66.setText("男");            } else if (d == 2) {                jl66.setText("女");            } else {                jl66.setText("Cann't found any information");            }            if (a != null) {                for (int i = 6; i < 14; i++) {                    jl77.setText((String)list.get(0).substring(6,14));                }            } else {                jl77.setText("Cann't found any information");            }        }    }