Scala way to add to List if not null

Question

Scala newbie here...

Doing below on address java object with getStLine*() methods... yields a List with empty strings for the empty strings returned. whats the Scala way to cleanly not add empty strings to a list.

val streets = List[String](addr.getStLine1, addr.getStLine2, addr.getStLine3)

Konstantin · Accepted Answer · 2013-12-05 17:01:01Z

5

Looks like you're explicitely adding strings to list, I don't think you'd be able to easily avoid adding empty strings without custom derived list implementation. On the other hand you can easily filter out empty strings after the fact.

scala> val z = List("one", "", "three")
z: List[java.lang.String] = List(one, "", three)

scala> z.filter(p=> p!=null && !p.equals(""))
res2: List[java.lang.String] = List(one, three)

answered Dec 5, 2013 at 17:01

Konstantin

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6 Comments

om-nom-nom Over a year ago

By the way in Scala you usually compare strings with == not like in Java.

Alan Jurgensen Over a year ago

Yes, I do like the looks of this: streets.filterNot(s => s == null || s == "" )

n1r3 Over a year ago

More idomatic : z.filter(!_.isEmpty)

Konstantin Over a year ago

@n1r3 that'll throw null pointer, isEmpty checks for 0 length, not nulls

n1r3 Over a year ago

the question is "cleanly not add empty strings", I didn't see anything about null in the question.

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