Firebase Docs Reference Interface: InstanceBuilder functions.database.InstanceBuilder interface static The Firebase Realtime Database instance builder interface. Access via functions.database.instance(). Method ref ref() returns functions.database.RefBuilder Returns non-null functions.database.RefBuilder Firebase Realtime Database reference builder interface. Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 3.0 License, and code samples are licensed under the Apache 2.0 License. For details, see our Site Policies. Java is a registered trademark of Oracle and/or its affiliates. Last updated April 5, 2018.