code: public synchronized boolean updateExpirationInHeader(Object key, long expirationTime, long validatorExpirationTime)
                      throws IOException,
                      EOFException,
                      FileManagerException,
                      ClassNotFoundException,
                      HashtableOnDiskException {
          if (filemgr == null) {
              throw new HashtableOnDiskException("No Filemanager");
          }
  
          if (key == null)
              return false; // no null keys allowed
  
          HashtableEntry entry = findEntry(key, RETRIEVE_KEY, !CHECK_EXPIRED);
          if (entry == null)
              return false; // not found
  
          //
          // Seek to point to validator expiration time field in the header
          filemgr.seek(entry.location +
                       DWORDSIZE + // room for next
                       SWORDSIZE); // room for hash
          filemgr.writeLong(validatorExpirationTime); // update VET
          /*
           * comment out the code below because the expiration time does not change
           * filemgr.writeInt(0);
           * filemgr.writeInt(entry.cacheValueHashcode); // update cache value hashcode
           * filemgr.writeLong(entry.first_created); // update first created (not neccessary but move to pointer
           * filemgr.writeLong(expirationTime); // update RET
           */
          htoddc.returnToHashtableEntryPool(entry);
          return true;
      }
docs: This method is used to update expiration times in disk entry header