What should a Scala developer know about Java and / or the JVM?


So up until about 6 months ago, most of my work (big graph processing) consisted of Python and C++. Up to that point, and even now, I had not written any Java whatsoever.. I had seen the language and was familiar with the syntax (having come from a C/C++ background), and liked the idea of the JVM, but never actually written any substantial amount of Java.

When I picked up Scala, I loved it, OOP and functional programming features all in one, and it being on the JVM was great. I've been constantly striving to improve my Scala and have been playing with Akka, and still loving it. However, at times, perhaps it is just me overthinkng it, but I feel I should learn some more about Java and/or the JVM.

I've heard from many that Scala should be considered a separate language from Java, much like C++ to C. Perhaps you may feel the same way, and perhaps learning Java is more or less disjoint from learning Scala, but I'm feeling learning more about the JVM (e.g. JIT compilation, type erasure) would be helpful?


  1. The JVM executes Bytecode and it is definately helpful to know how this works, just as it is sometimes helpful to know how C/C++ method invocations work or how classes are initialized; because sometimes it matters and cannot be abstracted away.

  2. Java is the prime language for the JVM, and it is helpful to be able to read Java to some extent if you need to use Java classes directly. And this may happen quite often; only a few examples:

    • you need to use some third party Java library (and there are tons)
    • working with Properties
    • you need to do something special in Swing which is not supported by the Scala-Swing wrapper
    • also sources explaining stuff for 1) will most probably use Java examples

But my advice is not to study it in advance - you'll pick it up when you need it.