=========
Guava 21
Important: Guava 21.0 requires Java 8. If you need Java 6, 7 or Android compatibility, use Guava 20.0 for now. Guava 22.0 and on will introduce a Java 6/Android compatible backport of Guava that includes all of the latest changes that don't require Java 8.
Article 1 : Introduction to Guava21 common.collect package.