code: private ReadResultEntryBase createFutureRead(long streamSegmentOffset, int maxLength) {
          FutureReadResultEntry entry = new FutureReadResultEntry(streamSegmentOffset, maxLength);
          this.futureReads.add(entry);
          return entry;
      }
docs: Creates a ReadResultEntry that is a placeholder for data that is not in memory, or in storage, which has
  a starting offset beyond the length of the StreamSegment.
  
  @param streamSegmentOffset The Offset in the StreamSegment where to the ReadResultEntry starts at.
  @param maxLength           The maximum length of the Read, from the Offset of this ReadResultEntry.