code: public static void reverse(final char[] a, int fromIndex, int toIndex) {
          checkFromToIndex(fromIndex, toIndex, len(a));
  
          if (N.isNullOrEmpty(a) || a.length == 1) {
              return;
          }
  
          char tmp = 0;
  
          for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) {
              tmp = a[i];
              a[i] = a[j];
              a[j] = tmp;
          }
      }
docs: <p>
  Reverses the order of the given array in the given range.
  </p>
  
  @param a
  @param fromIndex
  @param toIndex