code: public Number reserveStreamId() {
          double d = 1.0d;
          for (; d < MAX_RESERVED_STREAMS; d++) {
              if (reservedStreams.add(d)) {
                  break;
              }
          }
          if (d == MAX_RESERVED_STREAMS) {
              throw new IndexOutOfBoundsException("Unable to reserve new stream");
          }
          return d;
      }
docs: {@inheritDoc}