public void geraSix(){
    MegaSenaController numberRandom = new MegaSenaController();
    numberRandom.megaSena();
    String groupFirst = numberRandom.getPrimary();
    groupText.setText(groupFirst);
}

MegaSenaController numberRandom = new MegaSenaController();
int qntNumeros = (int) spinner.getSelectedItem();
List<Integer> numeros = new ArrayList();

for (int aux=0 ; aux<=qntNumeros ; aux++) {
    numberRandom.megaSena();
    numeros.add(numberRandom.getPrimary());
}

for (var i = 0, max = max/*neste max voce deve pegar o valor que o usuario quer*/; i < max; i++) {
    //gera um numero aleatorio
}