Replace null values in a list with another value in Scala

Question

I'm attempting to replace the null elements of a Scala list with an empty value using map. I currently have:

val arr = Seq("A:B|C", "C:B|C", null)
val arr2 = arr.map(_.replaceAll(null, "") )

This gives me a NullPointerExpection. What is the best way to do this?

To truly understand the map function, I recommend learnyouahaskell.com/higher-order-functions. — Kevin Meredith
– Kevin Meredith, Commented Sep 20, 2016 at 17:33

Zyoma · Accepted Answer · 2016-09-20 16:55:45Z

9

You're trying to replace a null character in a string instead of replacing a null string in Seq. So here is a correct way:

val arr2 = arr.map(str => Option(str).getOrElse(""))

The Option here will produce Some(<your string>) if the value is not null and None otherwise. getOrElse will return your string if it's not null or empty string otherwise.

answered Sep 20, 2016 at 16:55

Zyoma

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3 Comments

som-snytt Over a year ago

More idiomatic: vs.mapConserve { case null => "" case x => x }

Zyoma Over a year ago

Actually it's not recommended to use null in Scala directly.

som-snytt Over a year ago

The data in question already uses null. It's not forbidden to use the null keyword; you just want to limit it to a boundary like this one, when ingesting data. And to keep null out of API. They want Option to be a value class to avoid needless creating Option objects as you do here; in that case, your expr would be more appetizing.

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