日期下拉列表，年月日分开的！！

package com.demo.exresice;

import java.awt.EventQueue;

public class A extends JFrame {

private JPanel contentPane;

/**
* Create the frame.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
A frame = new A();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public A() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
contentPane.setLayout(new FlowLayout(FlowLayout.LEFT));