Java Data Type How to - Constrain user to enter a time in a JTextField

Question

We would like to know how to constrain user to enter a time in a JTextField.
Answer

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.ParseException;
/*from  w ww .  j  a v a  2 s  .c o m*/
import javax.swing.JFormattedTextField;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;
import javax.swing.text.MaskFormatter;

public class Main {
  public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
      @Override
      public void run() {
        new FormattedTextFieldExample();
      }
    });
  }

}

class FormattedTextFieldExample {

  public FormattedTextFieldExample() {
    initComponents();
  }

  private void initComponents() {
    JFrame frame = new JFrame("JFormattedTextField Example");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    MaskFormatter mask = null;
    try {
      mask = new MaskFormatter("##h##min##s");// the # is for numeric values
      mask.setPlaceholderCharacter('#');
    } catch (ParseException e) {
      e.printStackTrace();
    }
    final JFormattedTextField timeField = new JFormattedTextField(mask);

    // ActionListener for when enter is pressed
    timeField.addActionListener(new ActionListener() {
      @Override
      public void actionPerformed(ActionEvent ae) {
        Object source = ae.getSource();
        if (source == timeField) {
          // parse to a valid time here
          System.out.println(timeField.getText());
        }
      }
    });
    frame.add(timeField);
    frame.pack();
    frame.setVisible(true);
  }
}