我想创建类似下图的内容,当用户从组合框选项中选择年份、月份和日期时,这些操作将更改标题,并且必须根据所选数据进行更改,这很简单,我还是新手

到目前为止,我已经做到了,问题是它不起作用,我怎么能做到呢?,你能帮我一下吗?

import java.awt.GridLayout;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import javax.swing.JButton;

import javax.swing.JComboBox;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JOptionPane;

import javax.swing.JTextField;

public class DateForm_Complete extends JFrame {

private JLabel year, month, day;

private JComboBox cmonth, cday, cyear;

public DateForm_Complete() {

setTitle("Date Selection");

setSize(400,100);

setupWidgets();

setVisible(true);

}

private void setupWidgets() {

year= new JLabel("Year");

month= new JLabel("Month");

day= new JLabel("Day");

cyear= new JComboBox();

cmonth= new JComboBox();

cday= new JComboBox();

setLayout(new GridLayout (2,3));

add(year); add(month); add(day);

add(cyear); add(cmonth); add(cday);

for (int i=1900; i<2019; i++)

{

cyear.addItem(i);

}

String months[] = {"January","February","March","April","May","June","July","August","September","October","November","December"};

for (int i=0; i<12; i++)

{

cmonth.addItem(months[i]);

}

for (int i=1; i<32; i++)

{

cday.addItem(i);

}

setupEvents();

}

private void setupEvents() {

setDefaultCloseOperation(EXIT_ON_CLOSE);

cyear.addActionListener(new ActionListener() {

@Override

public void actionPerformed(ActionEvent ev) {

JComboBox combo = (JComboBox)ev.getSource();

String texty = (String)combo.getSelectedItem();

}

});

cmonth.addActionListener(new ActionListener() {

@Override

public void actionPerformed(ActionEvent ev) {

JComboBox combo = (JComboBox)ev.getSource();

String textm = (String)combo.getSelectedItem();

}

});

cday.addActionListener(new ActionListener() {

@Override

public void actionPerformed(ActionEvent ev) {

JComboBox combo = (JComboBox)ev.getSource();

String textd = (String)combo.getSelectedItem();

}

});

setTitle("Today is "+ texd+ "of "+ textm + "of " +texty);

}

public static void main(String[] args) {

new DateForm_Complete();

}

}