LimitedPrivs.java

public static void initWithLimitedPrivileges() {
  // Initialize the app with a custom auth variable, limiting the server's access
  Map<String, Object> auth = new HashMap<String, Object>();
  auth.put("uid", "my-service-worker");

  FirebaseOptions options = new FirebaseOptions.Builder()
    .setCredentials(GoogleCredentials.getApplicationDefault())
    .setDatabaseUrl("https://databaseName.firebaseio.com")
    .setDatabaseAuthVariableOverride(auth)
    .build();
  FirebaseApp.initializeApp(options);
}