QuickSort Not working PerFect Help me

- one Array as input - another one as output. You can see the result better doing it that way. the output array should be class member, so you do not need to pass it around that much.

- consistent naming of variables. You are changing around the names, using a lot of i and j. That's more confusion than needed. Keep it straight, one name for one variable that is fixed for all times. Also choose longer names, i and j are considered for counting in loops only. how about "iNext" ?

Here's the code for quick sort

public class QuickSort 
{
   int partition(int arrNum[], int low, int high)
   {
      int pivot = arrNum[high]; 
      int a = (low - 1); // smaller element index
      for(int b = low; b < high; b++)
      {
         // condition to check current element is smaller than or equal to pivot
         if(arrNum[b] <= pivot)
         {
            a++;
            // swapping arrNum[a] and arrNum[b]
            int temp = arrNum[a];
            arrNum[a] = arrNum[b];
            arrNum[b] = temp;
         }
      }
 
      // swapping arrNum[a + 1] and arrNum[high]
      int temp = arrNum[a + 1];
      arrNum[a + 1] = arrNum[high];
      arrNum[high] = temp;
 
      return a + 1;
   }
 
   void sortNumber(int arr[], int low, int high)
   {
      if(low < high)
      { 
         int part = partition(arr, low, high);
         // Recursive function sort elements before partition and after partition
         sortNumber(arr, low, part - 1);
         sortNumber(arr, part + 1, high);
      }
   }
 
   // printing utility function
   static void printingArray(int arr[])
   {
      int num = arr.length;
      for(int a = 0; a < num; ++a)
         System.out.print(arr[a] + " ");
      System.out.println();
   }
 
   public static void main(String[] args) 
   {
      int arr[] = {33, 36, 63, 34, 45, 78};
      int n = arr.length;
 
      QuickSort qs = new QuickSort();
      qs.sortNumber(arr, 0, n - 1);
 
      System.out.println("Quicksort sorted array : ");
      printingArray(arr);
   }
}