+ void onDataTreeChanged(@NonNull Collection<DataTreeModification<T>> changes);
+
+ /**
+ * Invoked only once during registration of the listener if there was no data in the conceptual data tree
+ * for the supplied path, which was used to register this listener, and after this
+ * {@link #onDataTreeChanged(Collection)} would always be invoked for data changes.
+ *
+ * <p>
+ * Default implementation does nothing and is appropriate for users who do not care about ascertaining
+ * initial state.
+ */
+ default void onInitialData() {
+ //no-op
+ }