CODEWITHSUNDEEP
javacollectionsapache-commons-collection
wrschneider
wrschneider

Reputation: 18780

null-safe Collection contains method

What's the best way to do null-safe contains on a Java collection?

in other words - 

 if (collection != null && collection.contains(x))

?

I was hoping Apache commons-collections had something like CollectionUtils.contains(collection, x) that would simply return false if the collection was null, as there is with size(), which treats null like an empty collection.

However, it seems like there is no such thing - did I just miss it?

Upvotes: 16

Views: 20957

Answers (2)

Ariel
Ariel

Reputation: 26773

Do it like this:

CollectionUtils.emptyIfNull(collection).contains(x)

There is also an equivalent version for SetUtils, MapUtils, ListUtils, etc.

This code is longer, so it seems to me it's mainly useful when you need a single expression for a Lambda.

Upvotes: 3

Thorn G
Thorn G

Reputation: 12766

You should instead be applying the Null Object Pattern here and use an empty collection, rather than a null collection. Of course, perhaps this is appropriate for your problem, but without more context it's hard to tell. In other words, I think you are solving the wrong problem -- why might collection be null in the first place?

Upvotes: 11

Related Questions