// generate prime numbers on 'Generate Prime Numbers' Button click
  @FXML
  private void generatePrimeNumbers() {
    bitsValue = valueBitsPrimary.getText(); // get a bits value entered by the user
    // firstPrime = firstPrimary.getText();
    // secondPrime = secondPrimary.getText();

    if (bitsValue.trim().equals("")) {

      makeAlert(
          "You have not selected a bits value!!",
          "Please select a bits value to generate prime number.");
      return; // if the bits value are not entered in the field, break the function and do not
      // proceed further
    }

    rsa.generatePrimes(bitsValue);

    // get first prime number
    firstPrimary.setText(rsa.getFirstPrime());
    // get second prime number
    secondPrimary.setText(rsa.getSecondPrime());
  }