code: public static void shuffleArray(int[] ar)
      {
          Random rnd = new Random();
          for (int i = ar.length - 1; i > 0; i--)
          {
              int index = rnd.nextInt(i + 1);
              // Simple swap
              int a = ar[index];
              ar[index] = ar[i];
              ar[i] = a;
          }
      }
docs: Fisher–Yates shuffle
  
  @param ar