code: protected synchronized void readFile() {
          if (realmFile != null && realmFile.exists() && (realmFile.lastModified() != lastModified)) {
              lastModified = realmFile.lastModified();
              try {
                  Preconditions.checkArgument(realmFile.canRead(), "The file '{}' can not be read!", realmFile);
                  Config config = ConfigFactory.parseFile(realmFile);
                  super.setup(config);
              } catch (Exception e) {
                  log.error("Failed to read {}", realmFile, e);
              }
          }
      }
docs: Reads the realm file and rebuilds the in-memory lookup tables.