https://chikuwa-tech-study.blogspot.com/2021/05/java-quick-sort.html

QuickSort.java

public class QuickSort {

    public static void sort(int[] data) {
        sort(data, 0, data.length - 1);
    }

    private static void sort(int[] data, int startIndex, int endIndex) {
        if (startIndex >= endIndex) {
            return;
        }
        
        int left = startIndex + 1;
        int right = endIndex;
        while (true) {
            while (data[left] < data[startIndex] && left < endIndex) {
                left++;
            }
            
            while (data[right] > data[startIndex] && right > startIndex) {
                right--;
            }

            if (left < right) {
                swap(data, left, right);
            } else {
                swap(data, startIndex, right);
                break;
            }
        }

        sort(data, startIndex, right - 1);
        sort(data, right + 1, endIndex);
    }

    private static void swap(int[] array, int index1, int index2) {
        int tmp = array[index1];
        array[index1] = array[index2];
        array[index2] = tmp;
    }
}