Quicksort Algorithm throws StackOverflowException

For a homework assignment, I have to write an implementation of the QuickSort algorithm and use this to sort a list with 100k numbers in some random order.

In the first part of the assignment, I have to use the first item of the array as the pivot element. This indeed returns a sorted list. However, for the second part of the assignment I have to use the last item as the pivot, which results in a StackOverflowException. When I try it in a smaller collection of 8 records, it DOES work correctly. I've been looking at my code but I can't figure out where I'm making a mistake. Any help would be greatly appreciated. My code is as follows:

public class QuickSort {
 
     private QuickSortStrategyEnum quickSortStrategy;
 
     public QuickSort(QuickSortStrategyEnum quickSortStrategy) {
 
         this.quickSortStrategy = quickSortStrategy;
     }
 
     public List<Integer> sortIntegerArray(List<Integer> arrayList, int left, int right) {
 
         if ( left >= right ) {
             return arrayList;
         }
 
         int i = partition(arrayList, left, right);
 
         if (i <= right) {
 
             int pivotNew = partition(arrayList, i, right);
             int pivotIndex = arrayList.indexOf(pivotNew);
 
             arrayList = sortIntegerArray(arrayList, left , pivotIndex - 1);
             arrayList = sortIntegerArray(arrayList, pivotIndex + 1, right);
         }
 
         return arrayList;
     }
 
     private int partition(List<Integer> arrayList, int left, int right) {
 
         int pivot = getPivot(arrayList, left, right);
         int i = left + 1;
 
         for (int j = i; j <= right; j++) {
 
             if (arrayList.get(j) < pivot) {
 
                 Collections.swap(arrayList, j, i);
                 i++;
             }
         }
 
         Collections.swap(arrayList, left, i - 1);
         return i;
     }
 
     private int getPivot(List<Integer> arrayList, int left, int right) {
 
         int pivot = 0;
 
         switch (quickSortStrategy) {
 
             case FIRST:
             pivot = arrayList.get(left);
             break;
 
             case LAST:
             pivot = arrayList.get(right);
             break;
         }
         return pivot;
     }
 
 }
 

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