Guava is a suite of core and expanded libraries that include utility classes, google's collections, io classes, and much much more. Guava has only one code dependency - javax.annotation, per the JSR-305 spec.

Checkstyle is a development tool to help programmers write Java code that adheres to a coding standard

Google client library for accessing Google APIs, providing OAuth2 support and request/response handling.

Google HTTP Client Library for Java. Functionality that works on all supported Java platforms, including Java 7 (or higher) desktop (SE) and web (EE), Android, and Google App Engine.

Google Auth Library For Java OAuth2 HTTP

Jackson 2 Extensions to The Google HTTP Client Library For Java.

GSON Extensions to The Google HTTP Client Library For Java.

Google OAuth Client Library for Java. Functionality that works on all supported Java platforms, including Java 7 (or higher) desktop (SE) and web (EE), Android, and Google App Engine.

This is the official Firebase Admin Java SDK. Build extraordinary native JVM apps in minutes with Firebase.

Java 6 (and Higher) Extensions to The Google OAuth Client Library For Java.

Jackson Extensions to The Google HTTP Client Library For Java.