As Java 9 has been released few days ago, I went through the What's New to see if there is something useful in the context of Competitive Programming. And I didn't find much, just these 2 enhancements:

• new static factory methods on the List, Set, and Map interfaces (returning immutable instances of those collections), for example: Set<String> alphabet = Set.of("a", "b", "c");

• internal String representation as array of bytes (8 bit) instead of array of chars (16 bit) in case the string contains only Latin-1 characters (which is normally the case in Competitive Programming); this would reduce memory consumption almost by half in String problems, and I wonder what would be the impact on performance.

As a personal note, I feel like Java is still light years behind Scala (which unfortunately is broken on CF for 2 months already) for writing CP code, even though both of them run on the same JVM. Just please, don't start language flame wars, unless you have tried both :)