Write the method

int doubles(ArrayList<Integer> list1, ArrayList<Integer> list2)

which takes two integer reading lists as parameters. 
The method returns the number of elements found in both list 1 and list 2.


Example method call:
public static void main(String[] args){
    ArrayList<Integer> list1 = new ArrayList<>();
    ArrayList<Integer> list2 = new ArrayList<>();

    list1.add(1);
    list1.add(2);
    list1.add(3);

    list2.add(3);
    list2.add(4);
    list2.add(5);
    list2.add(6);

    int t = doubles(list1, list2);
    System.out.println("Doubles: " + t);
}

Program outputs:
Doubles: 1










import java.util.Random;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.stream.Collectors;

public class Test{
    public static void main(String[] args){
        final Random r = new Random();
        
        test(new int[]{1,2,3,4,5,6,7,8}, new int[]{5,6,7,8,9,10,11,12});
        test(new int[]{10,20,30,40,50,60,70}, new int[]{25,30,35,40,45,50});
        test(new int[]{1,9,2,8,3,7,4,6}, new int[]{10,11,12,3,14,15,16,7,4,99,1,98,2});
    }
    
    public static void test(int[] l1, int[] l2) {
        ArrayList<Integer> list1 = new ArrayList<>();
        for (int a : l1) {
            list1.add(a);
        }
        
        ArrayList<Integer> list2 = new ArrayList<>();
        for (int a : l2) {
            list2.add(a);
        }
        
        System.out.println("Testing with lists ");
        System.out.println("" + list1);
        System.out.println("and");
        System.out.println("" + list2);
        System.out.println("Doubles: " + doubles(list1, list2));
        System.out.println("");
    }
    


    //ADD
    //ASSUME BOTH list1, list2 do not contain dupe elements
    public static int doubles(ArrayList<Integer> list1, ArrayList<Integer> list2) {
        int count = 0;

        // // check Double dtype of each element
        // for (int i = 0; i < list1.size(); i++) {
        //     if (list1.get(i) instanceof Double) { 
        //         count++;
        //     }
        // }
        // for (int i = 0; i < list2.size(); i++) {
        //     if (list2.get(i) instanceof Double) { 
        //         count++;
        //     }
        // }

        for (int i: list1) {
            if (list2.contains(i)) {
                count++;
            }
        }
        return count;
    }





}








Testing with lists 
[1, 2, 3, 4, 5, 6, 7, 8]
and
[5, 6, 7, 8, 9, 10, 11, 12]
Doubles: 4

Testing with lists 
[10, 20, 30, 40, 50, 60, 70]
and
[25, 30, 35, 40, 45, 50]
Doubles: 3

Testing with lists 
[1, 9, 2, 8, 3, 7, 4, 6]
and
[10, 11, 12, 3, 14, 15, 16, 7, 4, 99, 1, 98, 2]
Doubles: 5