import java.awt.Dimension; import java.awt.FlowLayout; import java.awt.HeadlessException; import java.awt.event.KeyAdapter; import java.awt.event.KeyEvent; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JTextField; public class Main extends JFrame { public Main() throws HeadlessException { setSize(200, 200); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setLayout(new FlowLayout(FlowLayout.LEFT)); JLabel usernameLabel = new JLabel("Username: "); JTextField usernameTextField = new JTextField(); usernameTextField.setPreferredSize(new Dimension(100, 20)); add(usernameLabel); add(usernameTextField); usernameTextField.addKeyListener(new KeyAdapter() { public void keyReleased(KeyEvent e) { JTextField textField = (JTextField) e.getSource(); String text = textField.getText(); textField.setText(text.toUpperCase()); } public void keyTyped(KeyEvent e) { } public void keyPressed(KeyEvent e) { } }); } public static void main(String[] args) { new Main().setVisible(true); } }