Some people advocate their preferred language as the only way to enlightenment and productivity boosts way in the two digit percentage range compared to another language in the same category. I don't believe it. (It's probably true when you compare things like Java and Assembler, but few do that)

There are others that tell you the language doesn't matter at least not between languages like Scala and Java. I think they are wrong as well. The reason is: Although I don't actually use Scala during my day job it does affect my Java Coding. Here are some of the things I noticed.

So go ahead and learn a new language. Even if you can't use it in your normal job. You still will learn useful stuff. But be warned. I might as well make you hate parts of your day job:

I really, really hate semicolons, primitives, arrays and collection APIs without higher order functions. And switching on Strings is a joke.