He could probably try to justify: Scala idioms to structure code tend to be faster than Java idioms.
Re:Is Scala really Faster than Java?
by eevilspock on Tuesday June 21, 2011 @11:26AM
(#2679122)
Or argue that the Scala language provides more information to the static compiler allowing it to produce better byte code. Has anyone done that analysis?
In general, the Java static compiler generates pretty poor-performing bytecode, no matter how much useful info you give it. This is by design, and relies on HotSpot to provide the necessary optimisations at runtime.
I'm no expert but I would assume that the Scala compiler is quite similar. Not much point in generating highly optimised bytecode when HotSpot will do the job for you.
Thankfully the author realizes this in his conclusion - "it seems that difference in implementations is the cause for difference in the time taken by Java/Scala programs".