When I developed the application for my talk on non-Java development for Android [1], I found that Scala performed as quickly as plain Java. However, it does use a bit more heap.

[1]: http://www.deepbluelambda.org/events/live/decaffeinated-robo...

I found this odd as well. I have always heard that it runs faster. For example: https://days2011.scala-lang.org/sites/days2011/files/ws3-1-H...

That paper explains that the Scala engineer performed numerous algorithmic improvements, whereas the Java one "refused" to (he reported somewhere else, on a mailing list? that he wasn't told it was for a paper). The paper also explains that using Scala idiomatic for-comprehensions produced very slow results.