Scala: Check for null for List

Question

I am new to Scala after coding for 10 years in Java. Still getting hold of functional programming. How can I check if the list is null or not? Code looks something like this:

val filterList = filters.map { filter =>
        //some operations
      }

//Other function

filterList.foldLeft(true)((result1, result2) => {

Now if filters is null then filterList is going to be null too.

Answer 1

If filters is null (which is different from being empty) then that indicates some pretty careless programing, but it can be handled.

val filterList = Option(filters).map(_.map { ...

Now filterList is of type Option[X] where X is the collection type for filters . Note the 1st map is to unwrap the Option and the 2nd map maps over the collection, except if filters was null , then the 2nd map is never invoked and the whole result is None .

Answer 2

val filterList = if(filters == null) Seq.empty[SomeType] else filters.map {...}

However, you should try to make sure it never gets to be null, because we try to avoid null variables in Scala. Use the Option[T] type, or empty collections instead