+ Inline functions Extension functions Properties Primary constructors First-class delegation Type inference Declaration-site variance & Type projections Range expressions Operator overloading Companion objects Data classes Separate interfaces for read-only and mutable collections Coroutines Singletons
javax.time Use ThreeTenBP - No streams Use RxJava - No lambdas, method refs, non-capturing anon classes Use Retrolambda - No try-with resources Use Retrolambda or minSDK=19