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

A couple of my favourites:

1. It took me a while to realise how truly useful Option is. A common mistake carried from Java is to use null to represent a field/variable that sometimes does not have a value. Recognise that you can use 'map' and 'foreach' on Option to write safer code.

2. Learn how to use 'map', 'foreach', 'dropWhile', 'foldLeft', ... and other handy methods on Scala collections to save writing the kind of loop constructions you see everywhere in Java, which I now perceive as verbose, clumsy, and harder to read.