code: protected Object mapRemove(Object key)
                      throws IOException,
                      EOFException,
                      FileManagerException,
                      ClassNotFoundException,
                      HashtableOnDiskException {
          if (key == null)
              return null; // no null keys allowed
  
          HashtableEntry e = findEntry(key, RETRIEVE_KEY, !CHECK_EXPIRED);
          if (e == null)
              return null; // not found
  
          Object answer = e.getValue();
          if (!remove(e)) {
              answer = null;
          }
          htoddc.returnToHashtableEntryPool(e);
          return answer;
      }
docs: ***********************************************************************
  remove(key) with Map semantics, for HTODMap. See comment to mapPut. We
  do not publicly advertise this interface.
  ************************************************************************