Java "lambda expressions not supported at this language level"
In IntelliJ IDEA:
In File Menu → Project Structure → Project, change Project Language Level to 8.0 - Lambdas, type annotations etc.
For Android 3.0+ Go File → Project Structure → Module → app and In Properties Tab set Source Compatibility and Target Compatibility to 1.8 (Java 8)
Screenshot:
You should change source code Language Level also on the Source tab (Modules part).
