> My understanding is that Java added a lot of functional programming

This is true, but needs more context. Java 8 added Stream API, which (at this time) was a fantastic breath of fresh air. However, the whole thing felt overengineered at many points, aka - it made complex things possible (collector chaining is admittedly cool, parallel streams are useful for quick-and-dirty data processing), but simple everyday things cumbersome. I cannot emphasize how tiring it was to have to write this useless bolierplate

  customers.stream().map(c -> c.getName()).collect(Collectors.joining(", "))

  customers.map(c -> c.getName()).join(", ")

It's such a blessing to be able to write in Scala

  customers.map(_.name).mkString(", ")

  customers.stream().map(c -> c.getName()).collect(Collectors.joining(", "))

It bothers me that majority of languages ignores a nice python approach. `', '.join(any_str_iterable)`. Instead of supporting join for myriads of containers there is a single str method.