public class CheckBoxTest extends JFrame{    private static final long serialVersionUID = 1L;    private JPanel panel1 = new JPanel();    private JPanel panel2 = new JPanel();    private JTextArea jt = new JTextArea(3,10);    private JCheckBox jc1 = new JCheckBox("1");    private JCheckBox jc2 = new JCheckBox("2");    private JCheckBox jc3 = new JCheckBox("3");    public CheckBoxTest() {        Container c = getContentPane();        setSize(200, 160);        setVisible(true);        setTitle("复选框的使用");        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);        c.setLayout(new BorderLayout());                c.add(panel1, BorderLayout.NORTH);        final JScrollPane scrollPane = new JScrollPane(jt);        panel1.add(scrollPane);                c.add(panel2, BorderLayout.SOUTH);        panel2.add(jc1);        jc1.addActionListener(new ActionListener() {            @Override            public void actionPerformed(ActionEvent e) {                // TODO Auto-generated method stub                if(jc1.isSelected()){                    jt.append("复选框1被选中\n");                }            }        });        panel2.add(jc2);        jc2.addActionListener(new ActionListener() {                        @Override            public void actionPerformed(ActionEvent e) {                // TODO Auto-generated method stub                if(jc2.isSelected()){                    jt.append("复选框2被选中\n");                }            }        });        panel2.add(jc3);        jc3.addActionListener(new ActionListener() {            @Override            public void actionPerformed(ActionEvent e) {                // TODO Auto-generated method stub                if(jc3.isSelected()){                    jt.append("复选框3被选中\n");                }            }        });    }    public static void main(String[] args) {        // TODO Auto-generated method stub        new CheckBoxTest();    }}