Filter Null items in Stream

Question

When using a Java Stream, sometimes null values can occur after mapping. Currently when these values need to be omitted, I use:

.stream()
.<other operations...>
.filter(element -> element != null)
.<other operations...>

For a more functional style a tiny helper method is quickly written:

public static <T> boolean nonNull(T entity) {
    return entity != null;
}

So that you can use a method reference instead:

.stream()
.<other operations...>
.filter(Elements::nonNull)
.<other operations...>

I could not find such a jdk method, even though I would suspect they have included one. Is there a different approach here? Or did they omit this for a reason?

Nothing in itself, but I prefer a method reference when this situation occurs in a pipeline using only method references. It felt like a combo breaker. — Boris van Katwijk, Mar 02 '16 at 08:02
Related: [Is there any difference between Objects::nonNull and x -> x != null?](https://stackoverflow.com/questions/25435056/is-there-any-difference-between-objectsnonnull-and-x-x-null) — Jeffrey Bosboom, Mar 02 '16 at 08:14
As a side note, the type parameter `` is obsolete for your `nonNull` method. It doesn’t change the fact that you can pass any object to it, so you can simply declare the parameter as `Object`. — Holger, Mar 02 '16 at 09:12
@Holger I think you mean "redundant" not "obsolete" but very good point! — Mateusz Dymczyk, Mar 02 '16 at 11:04
@Mateusz Dymczyk: that depends on whether it had a purpose in an older version of the code which I can’t decide, but yes, “redundant” is likely the better word. — Holger, Mar 02 '16 at 11:35
@Holger It was a leftover of stripping an existing utility stream map method which used T in its return type — Boris van Katwijk, Mar 02 '16 at 11:59

score 38 · Accepted Answer · answered Mar 02 '16 at 07:55

38

You can use Objects::nonNull from the Java8 SDK:

.stream()
.<other operations...>
.filter(Objects::nonNull)
.<other operations...>

answered Mar 02 '16 at 07:55

Mateusz Dymczyk

14,969
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Can't believe I overlooked that one! – Boris van Katwijk Mar 02 '16 at 11:21
@BorisvanKatwijk check out the whole Objects class, has some cool stuff :-) – Mateusz Dymczyk Mar 02 '16 at 13:30
Both `Objects.isNull()` and `Objects.nonNull()`, were introduced in `1.8`. I believe second method should have been better named as `Objects.isNotNull()` – Venkata Raju May 15 '18 at 10:16

Rahul Tripathi · Answer 2 · 2016-03-02T11:13:04.400

3

You can use the Objects::nonNull

Returns true if the provided reference is non-null otherwise returns false.

.stream()
.<other operations...>
.filter(Objects::nonNull)
.<other operations...>

edited Mar 02 '16 at 11:13

answered Mar 02 '16 at 07:56

Rahul Tripathi

168,305
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Filter Null items in Stream

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