code: public boolean clearDataBytes(String fullPath, int ifVersion)
      {
          ChildData data = currentData.get(fullPath);
          if ( data != null )
          {
              if ( (ifVersion < 0) || (ifVersion == data.getStat().getVersion()) )
              {
                  if ( data.getData() != null )
                  {
                      currentData.replace(fullPath, data, new ChildData(data.getPath(), data.getStat(), null));
                  }
                  return true;
              }
          }
          return false;
      }
docs: As a memory optimization, you can clear the cached data bytes for a node. Subsequent
  calls to {@link ChildData#getData()} for this node will return <code>null</code>.
  
  @param fullPath  the path of the node to clear
  @param ifVersion if non-negative, only clear the data if the data's version matches this version
  @return true if the data was cleared