code: protected void complete(ReadResultEntryContents readResultEntryContents) {
          Preconditions.checkState(!this.contents.isDone(), "ReadResultEntry has already had its result set.");
          CompletionConsumer callback = this.completionCallback;
          if (callback != null) {
              callback.accept(readResultEntryContents.getLength());
          }
  
          this.contents.complete(readResultEntryContents);
      }
docs: Completes the Future of this ReadResultEntry by setting the given content.
  
  @param readResultEntryContents The content to set.