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

I haven't adopted lazy vals and streams so far.

In the beginning, a common error (which the compiler finds) is to forget the semicolon in a for:

 for (a <- al;
      b <- bl
      if (a < b)) // ...

and where to place the yield:

 for (a <- al) yield {
     val x = foo (a).map (b).filter (c)
     if (x.cond ()) 9 else 14 
 }

instead of

 for (a <- al) {
     val x = foo (a).map (b).filter (c)
     if (x.cond ()) yield 9 else yield 14  // why don't ya yield!
 }

and forgetting the equals sign for a method:

 def yoyo (aka : Aka) : Zirp { // ups!
     aka.floskel ("foo")
 }