Comparing List<Integer> by index

Question

    List<Integer> listOne= new ArrayList<>();
    listOne.add(10);
    listOne.add(2);
    listOne.add(3);

    //Second Array

    List<Integer> listTwo= new ArrayList<>();
    listTwo.add(3);
    listTwo.add(7);
    listTwo.add(1);

I want to compare two List and give point to listOneor listTwo depending on which value is greater

[10, 2, 3] compare to [3, 7, 1]
if listOne.get(0) > listTwo.get(0) //add one point to listOne

if listOne.get(0) < listTwo.get(0) //add one point to listTwo

Here is my tested code

    static List<Integer> compareList(List<Integer> a, List<Integer> b) {
        ArrayList<Integer> output = new ArrayList<>();
        output.add(0, 0);
        output.add(1, 0);
        int out = output.get(0);
        int out2 = output.get(1);
        for (int i = 0; i < a.size(); i++) {
            if (a.get(i) > b.get(i)) {
                out = out + 1;
            } 
            if (a.get(i) < b.get(i)) {
                out2 = out2 + 1;
            } 
        }

        output.add(0, out);
        output.add(1, out2);
        return output;

    }

It works, but its not outputting the expected answer

expected output : 2 1 output am getting : 2 1 0 0

Answer 1

You are adding two 0s to the List, and then you are adding two more numbers at the start of the List, in addition to the 0s.

Either remove these statements:

output.add(0, 0);
output.add(1, 0);

and keep these statements unchanged:

output.add(0, out);
output.add(1, out2);

Or just change these statements:

output.add(0, out);
output.add(1, out2);

to:

output.set(0, out);
output.set(1, out2);

Answer 2

When you do

output.add(0, out);
output.add(1, out2);

You add items to indices 0 and 1, which push the previously entered zeroes to indices 2 and 3. output is now [2, 1, 0, 0].

Remove

output.add(0, 0);
output.add(1, 0);

And change out and out2 initialization to

int out = 0;
int out2 = 0;

Now you don't need to add the results by index either

output.add(out);
output.add(out2);

Answer 3

If you remove:

output.add(0, 0);
output.add(1, 0);

Works:

static List<Integer> compareList(List<Integer> a, List<Integer> b) {
    ArrayList<Integer> output = new ArrayList<>();
    int out = 0;
    int out2 = 0;
    for (int i = 0; i < a.size(); i++) {
        if (a.get(i) > b.get(i)) {
            out = out + 1;
        }
        if (a.get(i) < b.get(i)) {
            out2 = out2 + 1;
        }
    }

    output.add(0, out);
    output.add(1, out2);
    return output;
}