code: public ChangesItem pollAndMergeAll()
     {
        ChangesItem totalChanges = new ChangesItem();
  
        for (ChangesItem particularChanges = poll(); particularChanges != null; particularChanges = poll())
        {
           totalChanges.merge(particularChanges);
        }
  
        return totalChanges;
     }
docs: Merges all current existed changes into one single {@link ChangesItem} and return them.
  Don't care if after merge new entries will come.