Scala code often needs to deal with null references, unfortunately. Such is the price of Java interoperability. One of my favourite utility methods is:

def ?[A <: AnyRef](ref: A): Option[A] =
    if (ref eq null) None else Some(ref)

// e.g.
val value = ?(javaCallThatMayReturnNull()).getOrElse(defaultValue)

Scala 2.8 offers this using Option(ref) instead of ?(ref). However, I can’t figure out why the Scala 2.8 method accepts non-reference values as well.

Another simple thing that may come in handy is an extractor for non-null values:

object NotNull {
  def unapply[A <: AnyRef](ref: A): Option[A] =
      if (ref eq null) None else Some(ref)
}

What’s the advantage of using an extractor? Say you have a collection of references, some of which may be null, and you want to ignore the null references:

val xs = List("a", null, "b", null, null, "c", null)
// prints "List(a, b, c)"
println(for (NotNull(x) <- xs) yield x)