In Java Swing, you can use the JDatePicker component to display a calendar for date selection. Here's an example of how to use it:

First, you need to add the JDatePicker library to your project. You can download it from here: https://github.com/JDatePicker/JDatePicker

Once you have the library, you can create a JDatePicker component and add it to your UI. Here's an example:

import java.awt.FlowLayout;
import java.util.Calendar;
import java.util.Date;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

import org.jdatepicker.JDatePicker;
import org.jdatepicker.impl.JDatePanelImpl;
import org.jdatepicker.impl.JDatePickerImpl;
import org.jdatepicker.impl.UtilCalendarModel;

public class DatePickerExample {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            // Create a panel with a flow layout
            JPanel panel = new JPanel(new FlowLayout());

            // Create a UtilCalendarModel with the current date
            UtilCalendarModel model = new UtilCalendarModel();
            model.setDate(Calendar.getInstance().get(Calendar.YEAR), Calendar.getInstance().get(Calendar.MONTH), Calendar.getInstance().get(Calendar.DAY_OF_MONTH));

            // Create a JDatePanel with the UtilCalendarModel
            JDatePanelImpl datePanel = new JDatePanelImpl(model);

            // Create a JDatePicker with the JDatePanel
            JDatePicker datePicker = new JDatePickerImpl(datePanel);

            // Add the JDatePicker to the panel
            panel.add(datePicker);

            // Create a frame and add the panel to it
            JFrame frame = new JFrame("Date Picker Example");
            frame.add(panel);
            frame.pack();
            frame.setVisible(true);
        });
    }
}

In this example, we create a JPanel with a FlowLayout, which will contain the JDatePicker component. We then create a UtilCalendarModel with the current date, and a JDatePanelImpl with the UtilCalendarModel. Finally, we create a JDatePickerImpl with the JDatePanelImpl, and add it to the panel.

When you run this example, you will see a window with a JDatePicker component showing the current date. You can click on the calendar icon to display the calendar and select a different date. The selected date will be displayed in the JDatePicker component.