ListOfListService class

import java.util.ArrayList;

public class ListOfListService {
    public static boolean contains(ArrayList<ArrayList<Integer>> list, Integer target) {
        if (list == null) {
            return false;
        }
        // iterate through every sublist of list
        for (int i = 0; i < list.size(); i++) {
            // checking wheter sublist contain a target or not if yes return true
            if (list.get(i).contains(target))
                return true;

        }
        return false;

    }

    public static Integer getItem(ArrayList<ArrayList<Integer>> list, int i, int k) {
        if (list == null) {
            return null;
        }
        if (i >= 0 && i < list.size() && k < list.get(i).size()) {
            return list.get(i).get(k);
        }
        return null;
    }

    public static boolean isSubListNotNull(ArrayList<ArrayList<Integer>> list, int i) {
        if (list == null) {
            return false;
        }
        // checking boundary
        if (i >= 0 && i < list.size()) {
            // taking sublist from list and testing its size
            ArrayList<Integer> arrayList = list.get(i);
            if (arrayList != null) {
                return true;
            }
        }
        return false;

    }

    public static Integer getFirstItem(ArrayList<ArrayList<Integer>> list) {
        if (list == null)
            return null;
        // checking boundary
        if (list.size() == 0 || list.get(0).size() == 0) {
            return null;
        }
        // returning first element
        return list.get(0).get(0);

    }
}