docs: public final static int packBytesAfter1(int unicodeScalar, int utf8Len)
      {
          int packed_chars;
  
          switch (utf8Len) {
          default:
              throw new IllegalArgumentException("pack requires len > 1");
          case 2:
              packed_chars = getByte2Of2(unicodeScalar);
              break;
          case 3:
              packed_chars  = getByte2Of3(unicodeScalar);
              packed_chars |= getByte3Of3(unicodeScalar) << 8;
              break;
          case 4:
              packed_chars = getByte2Of4(unicodeScalar);
              packed_chars |= getByte3Of4(unicodeScalar) << 8;
              packed_chars |= getByte4Of4(unicodeScalar) << 16;
              break;
          }
          return packed_chars;
  
      }