Quick Sort in Java

//To run this fucking code just pree right click then run code or Shift + F6

import java.util.Arrays;

public class QuickSort {

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

    private void sort(int[] arr, int start, int end) {

        if (start >= end) {
            return;
        }

        //Parititon
        int boundary = partition(arr, start, end);
        //Sort left 
        sort(arr, start, boundary - 1);
        //Sort right
        sort(arr, boundary + 1, end);
    }

    private int partition(int[] arr, int start, int end) {
        int pivot = arr[end];
        int boundary = start - 1;

        for (int i = start; i <= end; i++) {
            if (arr[i] <= pivot) {
                swap(arr, i, ++boundary);
            }
        }
        return boundary;
    }

    private void swap(int[] arr, int index1, int index2) {
        int temp = arr[index1];
        arr[index1] = arr[index2];
        arr[index2] = temp;
    }

    public static void main(String[] args) {

        int[] nums = {-1, -3, -2, 0, 1, 3, 6, 9, 2, -99, 99};

        QuickSort sort = new QuickSort();
        sort.sort(nums);

        System.out.println(Arrays.toString(nums));
    }

}