loop an array to group values for a total

How can I write a for loop that goes through an array and splits it into groups of 6. From there it should add the first group in the arrNumbers, then add the second group but reversed so { 6, 5, 4, 3, 2, 1 } to first group which is { 1, 2, 3, 4, 5, 6 } and then third group should be not reversed, but then if there is another group of 6, the set should be reversed to add. I don't know how to go about this. Any help will be appreciated. Below is my attempt

import java.util.Arrays;

public class arrayAdding{

     public static void main(String []args){
        int[] arrNumbers = new int[] { 1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6 };
        int[] newArrNumbers = new int[6];
        
        for(int i  = 0; i < arrNumbers.length ; i++){
            newArrNumbers[i < 6 ? i : (6 - (i % 6) - 1)] += arrNumbers[i];
        }
        System.out.println(Arrays.toString(newArrNumbers));
     }
}

Actual Result from my code:

newArrNumbers = [13, 12, 11, 10, 9, 8]

The required result should be:

newArrNumbers = [8, 9, 10, 11, 12, 13]

You can think like group of 12 elements and not reversed for the first 6 and reversed for the next 6.

• (i % 12) < 6 - First half - i % 6
• (i % 12) >= 6 - Second half(reversed) - (6 - (i % 6) - 1)

Code:

newArrNumbers[(i % 12) < 6 ? i % 6 : (6 - (i % 6) - 1)] += arrNumbers[i];

You can refer below code:

import java.util.*;

public class ArrayAdding {

public static void main(String []args){
Integer[] arrNumbers = new Integer[] { 1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6 };
int[] newArrNumbers = new int[6];
List<List<Integer>> partitions = ArrayAdding.splitArray(arrNumbers);
Iterator<List<Integer>> itr = partitions.iterator();
while (itr.hasNext()) {
List<Integer> next = itr.next();
if (next.size() < 6 )
itr.remove();
}
for(int i  = 0; i < partitions.size() ; i++){
if (i % 2 != 0) {
Collections.reverse(partitions.get(i));
}
}
for (List<Integer> partition : partitions) {
for (int j = 0; j < 6; j++) {
newArrNumbers[j] = partition.get(j) + newArrNumbers[j];
}
}
System.out.println(Arrays.toString(newArrNumbers));
}
private static List<List<Integer>> splitArray(Integer[] arrNumbers) {
int partitionSize = 6;
List<List<Integer>> partitions = new LinkedList<>();
List<Integer> originalList = Arrays.asList(arrNumbers);
for (int i = 0; i < originalList.size(); i += partitionSize) {
partitions.add(originalList.subList(i,
Math.min(i + partitionSize, originalList.size())));
}
return partitions;
}}