docs: public synchronized boolean containsKey(Object key)
                      throws FileManagerException,
                      ClassNotFoundException,
                      IOException,
                      HashtableOnDiskException {
          if (filemgr == null) {
              throw new HashtableOnDiskException("No Filemanager");
          }
  
          HashtableEntry e = findEntry(key, RETRIEVE_KEY, !CHECK_EXPIRED);
          boolean found = (e != null);
          htoddc.returnToHashtableEntryPool(e);
          return found;
      }