Scala Lang
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Trial
Besides Java, Scala is the most mature language on the Java Virtual Machine. Its unique blend of object-oriented and functional language features and rich type system with advanced type inference enables one to write concise code.
It is fully interoperable with Java but has a big ecosystem of tools and frameworks on its own.
Scala provides one of the best high-level concurrency- and async features on the language level as well as on the framework level, making it the default choice of twitter and the like.
At AOE, we already use Scala in various projects to create scalable backend systems (Play, Akka) or for batch processing (Spark).