The Google OAuth Client Library for Java is designed to work with any OAuth service on the web, not just with Google APIs. The library is built on the Google HTTP Client Library for Java, and it supports Java 5 (or higher) standard (SE) and enterprise (EE), Android 2.1 (or higher), and Google App Engine.
For access to Google APIs, see the Google API Client Library for Java.
This is an open-source library, and you can access the source on GitHub. Contributions are welcome.
Features marked with the @Beta annotation at the class or method level are subject to change. They might be modified in any way, or even removed, in any major release. You should not use beta features if your code is a library itself (that is, if your code is used on the CLASSPATH of users outside your own control).
Deprecated non-beta features will be removed eighteen months after the release in which they are first deprecated. You must fix your usages before this time. If you don't, any type of breakage might result, and you are not guaranteed a compilation error.