code: public long stopStartTimer(long _expiryTime, Entry<K,V> e) {
      if ((_expiryTime > 0 && _expiryTime < Long.MAX_VALUE) || _expiryTime < 0) {
        throw new IllegalArgumentException("invalid expiry time, cache is not initialized with expiry: " + Util.formatMillis(_expiryTime));
      }
      return _expiryTime == 0 ? Entry.EXPIRED : _expiryTime;
    }
docs: Convert expiry value to the entry field value, essentially maps 0 to {@link Entry#EXPIRED}
  since 0 is a virgin entry. Restart the timer if needed.
  
  @param _expiryTime calculated expiry time
  @return sanitized nextRefreshTime for storage in the entry.