docs: public static final int parseUnsignedInt(CharSequence cs, int radix, int beginIndex, int endIndex)
      {
          check(cs, radix, NumberRanges.UnsignedIntRange, beginIndex, endIndex);
          int end = endIndex;
          int result = 0;
          int index = beginIndex;
          int cp = Character.codePointAt(cs, index);
          if (cp == '+')
          {
              index++;
          }
          if (index >= end)
          {
              throw new NumberFormatException("unparsable number "+cs.subSequence(beginIndex, endIndex));
          }
          while (index < end)
          {
              result *= radix;
              cp = Character.codePointAt(cs, index);
              int digit = Character.digit(cp, radix);
              if (digit == -1)
              {
                  throw new NumberFormatException("unparsable number "+cs.subSequence(beginIndex, endIndex));
              }
              result += digit;
              if (Character.isBmpCodePoint(cp))
              {
                  index++;
              }
              else
              {
                  index += 2;
              }
          }
          return result;
      }