Struggle against habits formed by Java when migrating to Scala

Question

What are the most common mistakes that Java developers make when migrating to Scala?

By mistakes I mean writing a code that does not conform to Scala spirit, for example

Answer 1

It's quite simple: Java programmer will tend to write imperative style code, whereas a more Scala-like approach would involve a functional style.

• That is what Bill Venners illustrated back in December 2008 in his post "How Scala Changed My Programming Style".
• That is why there is a collection of articles about "Scala for Java Refugees".
• That is how some of the SO questions about Scala are formulated: "help rewriting in functional style".