code: protected synchronized void readCredentialsFile() {
          if (realmFile != null && realmFile.exists() && (realmFile.lastModified() != lastModified)) {
              lastModified = realmFile.lastModified();
              try {
                  Map<String, String> credentials = readCredentialsURL(realmFile.toURI().toURL());
                  credentialsMap.clear();
                  credentialsMap.putAll(credentials);
              } catch (Exception e) {
                  log.error("Failed to read {}", realmFile, e);
              }
          }
      }
docs: Reads the credentials file and rebuilds the in-memory lookup tables.