Validate Jtextfield in Java Swing

In this section,you will learn how to validate the textfield by allowing only numbers to enter. For this purpose, we have used the keyEvent class.Using the method getKeyChar() of keyEvent class, we have allowed the user to enter only numeric digits from 0 to 9.If the user enters alphabets or other characters, an error message will get displayed.

Here is the code:

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class Validation extends JFrame {
	JTextField text;
	Container con;
	JLabel label;

	public Validation() {
		con = getContentPane();
		setBounds(0, 0, 500, 300);
		text = new JTextField(25);
		setLayout(new FlowLayout());
		con.add(new JLabel("Enter the number"));
		con.add(text);
		con.add(label = new JLabel());
		label.setForeground(Color.red);
		setDefaultCloseOperation(EXIT_ON_CLOSE);
		text.addKeyListener(new KeyAdapter() {
			public void keyPressed(KeyEvent EVT) {
				String value = text.getText();
				int l = value.length();
				if (EVT.getKeyChar() >= '0' && EVT.getKeyChar() <= '9') {
					text.setEditable(true);
					label.setText("");
				} else {
					text.setEditable(false);
					label.setText("* Enter only numeric digits(0-9)");
					
				}
			}
		});
		show();
	}

	public static void main(String[] args) {
		new Validation();
	}
}

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