code: public void sync() {
  		if (!validState) {
  			throw new InvalidStateException();
  		}
  		if (useMmap) {
  			syncAllMmaps();
  		}
  		if (fileChannel != null) {
  			try {
  				fileChannel.force(false);
  			} catch (Exception ign) {
  			}
  		}
  		if (callback != null) {
  			callback.synched();
  		}
  	}
docs: Forces any updates to this file to be written to the storage device that contains it.