private void okClick() {
  String userInput = textField.getText();
  int entered = -1;

  try {
    entered = Integer.parseInt(userInput);
  } catch (Exception e) {
    textField.setText("");
    JOptionPane.showMessageDialog(null, "You must enter an interger", "Error", JOptionPane.ERROR_MESSAGE);
    return;
  }

  if(hasDuplicates(entered) || entered < 1000  || entered > 9999) {
    textField.setText("");
    JOptionPane.showMessageDialog(null, "You must enter an interger with no duplicates digits and with 4-digits", "Error", JOptionPane.ERROR_MESSAGE);
    return;
  }

  nbGuesses++;

  int[] answer = bullsAndCows(entered);

  if (answer[0] == 4) {
    guessed = true;
  } else {
    updateText(entered + "\t\t\t\t" + answer[0] + " Bulls and " + answer[1] + " Cows");
  }

  if (guessed) {
    updateText("\n" + entered + "\n\nYou won after " + nbGuesses + " guesses!");
  }

  textField.setText("");
}