Question

Method: ArrayList<Integer> diff(ArrayList<Integer> list1, ArrayList<Integer> list2) diff() method accepts two ArrayLists of Integer and returns the union of elements in two lists. For example: list1 contains elements [1, 2, 3, 4, 5] list2 contains elements [3, 4, 5, 6, 7] Diff() method should return an array list with elements [1, 2, 3, 4, 5, 6, 7].

Answer 1

import java.util.ArrayList;
import java.util.Arrays;

public class UnionArrayLists {

    public static ArrayList<Integer> diff(ArrayList<Integer> list1, ArrayList<Integer> list2) {
        ArrayList<Integer> result = new ArrayList<>();
        for (int i = 0; i < list1.size(); i++) {
            if (!result.contains(list1.get(i))) {
                result.add(list1.get(i));
            }
        }
        for (int i = 0; i < list2.size(); i++) {
            if (!result.contains(list2.get(i))) {
                result.add(list2.get(i));
            }
        }
        return result;
    }

    public static void main(String[] args) {
        ArrayList<Integer> list1 = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));
        ArrayList<Integer> list2 = new ArrayList<>(Arrays.asList(3, 4, 5, 6, 7));
        System.out.println(diff(list1, list2));
    }
}