列表框组件

public class JComboBoxMode1Test extends JFrame{
    private static final long serialVersionUID = 1L;
    JComboBox<String> jc = new JComboBox<>(new MyComboBox());
    JLabel jl = new JLabel("请选择证件:");
    public JComboBoxMode1Test() {
        // TODO Auto-generated constructor stub
        setSize(new Dimension(160, 180));
        setVisible(true);
        setTitle("在窗口中设置下拉列表框");
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        Container cp = getContentPane();
        cp.setLayout(new FlowLayout());
        cp.add(jl);
        cp.add(jc);
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        new JComboBoxMode1Test();
    }

}

public class MyComboBox extends AbstractListModel<String> implements ComboBoxModel<String>{

    private static final long serialVersionUID = 1L;
    String selceteditem = null;
    String[] test = {"身份证","军人证","学生证","工作证"};
    

    @Override
    public int getSize() {
        // TODO Auto-generated method stub
        return test.length;
    }

    @Override
    public String getElementAt(int index) {
        // TODO Auto-generated method stub
        return test[index];
    }

    @Override
    public void setSelectedItem(Object item) {
        // TODO Auto-generated method stub
        selceteditem = (String)item;
    }

    @Override
    public Object getSelectedItem() {
        // TODO Auto-generated method stub
        return selceteditem;
    }
    
    public int getInex() {
        // TODO Auto-generated method stub
        for(int i=0;i<test.length;i++){
            if(test[i].equals(getSelectedItem()))
                return i;
        }
        return 0;
    }

}