code: public static int getDistance (@Nullable final char [] aStr1, @Nullable final char [] aStr2)
    {
      final int nLen1 = aStr1 == null ? 0 : aStr1.length;
      final int nLen2 = aStr2 == null ? 0 : aStr2.length;
  
      if (nLen1 == 0)
        return nLen2;
      if (nLen2 == 0)
        return nLen1;
  
      return _getDistance111 (aStr1, nLen1, aStr2, nLen2);
    }
docs: Get the distance of the 2 strings, using the costs 1 for insertion,
  deletion and substitution.
  
  @param aStr1
  First string.
  @param aStr2
  Second string.
  @return The Levenshtein distance.