Why does Scala language require you initialize a instance variable instead of relying on a default value?

Question

Scala language requires you initialize your instance variable before using it. However, Scala does not provide a default value for your variable. Instead, you have to set up its

Answer 1

You can apply the annotation when you specify it as a constructor argument. Also, you may need to use a meta-annotation to restrict which target the annotation you're using is applied to - see http://www.scala-lang.org/api/2.10.2-RC2/index.html#scala.annotation.meta.package

Your question about "relying on a default value" is somewhat unclear, though. Initialization using an underscore corresponds to assigning the value of the variable to null. What other default are you thinking of?