Keylistener for various Jtextfields

Question

I created a KeyListener for verification of a String typed, if it is in the bank. If it does, it sends an alert.

The question now is that I have about 50 jTextFields. It is possible to create a KeyListener that can be used for all jTextFields? Or I have to create one for each jTextField? 'Cause in my code I specify that I’m picking up the String of jTextField1 for example, not serving for what I need now.

Here is the code of KeyListener

private final KeyListener listener = new KeyListener() {

        @Override
        public void keyTyped(KeyEvent e) {

        }

        @Override
        public void keyReleased(KeyEvent e) {
            int max = 4;
            if (max == 4) {
                String digitado = jTextField1.getText().trim();
                if (digitado.length() == max) {
                    verificaStringDigitada(digitado);
                }
            }
        }

        @Override
        public void keyPressed(KeyEvent e) {

        }
    };

Method of making the check

public void verificaStringDigitada(String teste) {
        CarroDao carroDao = new CarroDao();
        List<Carro> carros = new ArrayList();
        carros = carroDao.consultarCarros();
        boolean ver = false;
        for (Carro carro : carros) {
            if (carros.contains(teste)) {
                ver = true;
            }
        }
        if (ver == false) {
            JOptionPane.showMessageDialog(null, "Verifique a digitação!");
            jTextField1.setText("");
        }
    }

Update1:

private final KeyAdapter listener = new KeyAdapter() {

        @Override
        public void keyReleased(KeyEvent e) {

            JTextField field = (JTextField) e.getSource();

            int max = 4;
            if (max == 4) {
                String digitado = field.getText().trim();
                if (digitado.length() == max) {
                    CarroDao carroDao = new CarroDao();
                    List<Carro> carros = new ArrayList();
                    carros = carroDao.consultarCarros();
                    boolean ver = false;
                    for (Carro carro : carros) {
                        if (digitado.equals(carro.getNumero())) {
                            ver = true;
                        }
                    }
                    if (ver == false) {
                        JOptionPane.showMessageDialog(null, "Verifique a digitação!");
                        field.setText("");
                    }
                }
            }
        }
    };

Answer 1

You can generalize this way:

private final KeyAdapter listener = new KeyAdapter() {

  @Override
  public void keyReleased(KeyEvent e) {

    JTextField field = (JTextField) e.getSource();

      int max = 4;
      if (max == 4) {
          String digitado = field.getText().trim();
          if (digitado.length() == max) {
              CarroDao carroDao = new CarroDao();
              List<Carro> carros = new ArrayList();
              carros = carroDao.consultarCarros();
              boolean ver = false;
              for (Carro carro : carros) {
                  if (carros.contains(digitado)) {
                      ver = true;
                 }
              }
              if (!ver) {
                  JOptionPane.showMessageDialog(null, "Verifique a digitação!");
                  field.setText("");
              }
          }
      }
  }
};

Or turning a class into a separate:

class MeuKeyAdapter extends KeyAdapter {

  @Override
  public void keyReleased(KeyEvent e) {

    JTextField field = (JTextField) e.getSource();

      int max = 4;
      if (max == 4) {
          String digitado = field.getText().trim();
          if (digitado.length() == max) {
              CarroDao carroDao = new CarroDao();
              List<Carro> carros = new ArrayList();
              carros = carroDao.consultarCarros();
              boolean ver = false;
              for (Carro carro : carros) {
                  if (carros.contains(digitado)) {
                      ver = true;
                 }
              }
              if (!ver) {
                  JOptionPane.showMessageDialog(null, "Verifique a digitação!");
                  field.setText("");
              }
          }
      }
  }  
}

The key to making the keylistener generic is to get an object of the type JTextField from the event itself, as is done on line JTextField field = (JTextField) e.getSource();. This way, it won’t matter to Listener if you apply to one or 100 different text fields.

I unified the method because I understood that if his goal is to check something typed in the text fields, it can be part of the system as well.