SWIFT

uitextfield set max length

extend UITextFieldDelegate

public func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    return range.location < 15
}

set jtextfield max length

textField = new JTextField();
    textField.addKeyListener(new KeyAdapter() {
        @Override
        public void keyTyped(KeyEvent e) {
            if (txtGuess.getText().length() >= 3 ) // limit to 3 characters
                e.consume();
        }
    });