The Question actually says it all.
The reason behind this question is I am about to start a small side project and want to do it in Scala. I am learning scala for the past one month and now I am comfortable working with it. The scala compiler itself is pretty slow (unless you use fsc). So how well does it perform on JVM? I previously worked on groovy and I had seen sometimes over performed than java. My Question is how well scala perform on JVM compared to Java. I know scala has some very good features(FP, dynamic lang, statically typed…) but end of the day we need the performance…
A majority of my work uses Scala as a high-performance language. If one really pays careful attention to performance, Scala is almost always nearly as good as Java (if not equivalent). If one is careless about e.g. object creations, it can be many times worse–as it can in Java if you use a library that is careless about object creations. (In fact, my Scala code is often faster than my Java code because I find it so much easier to make my highly optimized code convenient to use and reuse–but the Java would be as fast or faster if only I had more time and patience.)
If you want some data that demonstrates that Scala can be basically as fast as Java, check out the results on the Computer Languages Benchmark Game. (Another less useful but still interesting comparison for high-throughput multicore programming is Tim Bray’s Wide Finder 2. This is less useful because the algorithm is not defined in advance, so a large portion of the differences boil down to differences in algorithm.)