private void NumeroDeIncognitasKeyTyped(java.awt.event.KeyEvent evt) {

    char caracter = evt.getKeyChar();
    int limite;
    String cadena = NumeroDeIncognitas.getText() + caracter;
    if ((cadena.charAt(0) == '1')) {
        limite = 2;
    } else {
        limite = 1;
    }
    if (NumeroDeIncognitas.getText().length() == limite) {
        evt.consume();
    }
    if (cadena.charAt(0) == ',') {
        evt.consume();
    } else {
        if (((caracter < '0') || (caracter > '9')) && (caracter != KeyEvent.VK_BACK_SPACE)) {
            evt.consume();
        }
    }
}