import java.util.ArrayList;
import java.util.Random;

public class MillionNull {
    private static final int ONE_MILLION = 1_000_000;
    private static final int INNER_SIZE = 6;

    public static void main(String[] args) {
        final ArrayList<ArrayList<Integer>> myArrayListVariable = getObjects();

        myArrayListVariable.forEach(innerList -> { if (innerList.indexOf(null) >= 0) System.out.println(myArrayListVariable.indexOf(innerList));});
    }

    private static ArrayList<ArrayList<Integer>> getObjects() {
        final ArrayList<ArrayList<Integer>> myArrayListVariable = new ArrayList<>(ONE_MILLION);
        final Random random = new Random();
        for (int idx1 = 0; idx1 < ONE_MILLION; ++idx1) {
            final ArrayList<Integer> innerList = new ArrayList<>(INNER_SIZE);
            for (int idx2 = 0; idx2 < INNER_SIZE; ++idx2) {

                innerList.add(random.nextInt());
            }
            myArrayListVariable.add(innerList);
        }
        myArrayListVariable.get(ONE_MILLION / 2).set(3, null);
        return myArrayListVariable;
    }
}