Interview Sort Function

QuickSort

Java Code:

import java.util.*;
public class quickSort{
    public static void main(String [] args){
        int [] arr = new int[]{4,2,7,5,0,9,1};
        int low = 0;
        int high = arr.length-1;
        quickSort(arr, low, high);
        System.out.println(Arrays.toString(arr));
    }

    private static void quickSort(int [] arr, int low, int high){
        if(arr == null || arr.length == 0){
            return;
        }

        if(low >= high){
            return;
        }

        int pivot = arr[low + (high - low)/2];

        //make left < pivot, right > pivot
        int i = low;
        int j = high;
        while(i <= j){
            while(arr[i] < pivot){
                i++;
            }
            while(arr[j] > pivot){
                j--;
            }

            if(i <= j){
                int temp = arr[i];
                arr[i] = arr[j];
                arr[j] = temp;
                i++;
                j--;
            }
        }

        //recursively sort two sub arrays
        quickSort(arr, low, j);
        quickSort(arr, i, high);
    }
}