How can we make JTextField accept only numbers in Java?

By default, a JTextField can allow numbers, characters, and special characters. Validating user input that is typed into a JTextField can be difficult, especially if the input string must be converted to a numeric value such as an int.

In the below example, JTextField only allows entering numeric values.

Example

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class JTextFieldValidation extends JFrame {
   JTextField tf;
   Container container;
   JLabel label;
   public JTextFieldValidation() {
      container = getContentPane();
      setBounds(0, 0, 500, 300);
      tf = new JTextField(25);
      setLayout(new FlowLayout());
      container.add(new JLabel("Enter the number"));
      container.add(tf);
      container.add(label = new JLabel());
      label.setForeground(Color.red);
      setDefaultCloseOperation(EXIT_ON_CLOSE);
      setLocationRelativeTo(null);
      tf.addKeyListener(new KeyAdapter() {
         public void keyPressed(KeyEvent ke) {
            String value = tf.getText();
            int l = value.length();
            if (ke.getKeyChar() >= '0' && ke.getKeyChar() <= '9') {
               tf.setEditable(true);
               label.setText("");
            } else {
               tf.setEditable(false);
               label.setText("* Enter only numeric digits(0-9)");
            }
         }
      });
      setVisible(true);
   }
   public static void main(String[] args) {
      new JTextFieldValidation();
   }
}

Output