docs: private byte getConstantPoolStringFirstByte(final int cpIdx) throws ClassfileFormatException, IOException {
          final int constantPoolStringOffset = getConstantPoolStringOffset(cpIdx, /* subFieldIdx = */ 0);
          if (constantPoolStringOffset == 0) {
              return '\0';
          }
          final int utfLen = inputStreamOrByteBuffer.readUnsignedShort(constantPoolStringOffset);
          if (utfLen == 0) {
              return '\0';
          }
          return inputStreamOrByteBuffer.buf[constantPoolStringOffset + 2];
      }