How to check if element in groovy array/hash/collection/list?

Question

How do I figure out if an array contains an element? I thought there might be something like [1, 2, 3].includes(1) which would evaluate as true.

Can you find the index out also of where this equal element is in the list? — Arturo, Mar 30 '12 at 11:53

score 282 · Answer 1 · edited Feb 08 '16 at 14:33

282

Some syntax sugar

1 in [1,2,3]

edited Feb 08 '16 at 14:33

Mads Hansen

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answered Sep 15 '08 at 10:09

dahernan

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Careful. `def m = [a: true]; 'a' in m` → true yet `def m = [a: false]; 'a' in m` → false! – Jesse Glick Feb 01 '17 at 19:15
How do you negate this? – Big McLargeHuge Aug 07 '20 at 22:01
@BigMcLargeHuge `!(1 in [1,2,3])` – Leponzo Dec 13 '21 at 09:46
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The way to deal with `[a:false]` is to use contains. `[a: false].containsKey('a')` -> true – wiredniko Apr 12 '22 at 13:52
@Big McLargeHuge negation is also possible like this: `1 !in [1,2,3]` ([Membership operator Groovy](https://docs.groovy-lang.org/latest/html/documentation/#_membership_operator)) – david Aug 21 '23 at 10:32

score 158 · Accepted Answer · answered Sep 15 '08 at 20:44

158

.contains() is the best method for lists, but for maps you will need to use .containsKey() or .containsValue()

[a:1,b:2,c:3].containsValue(3)
[a:1,b:2,c:3].containsKey('a')

answered Sep 15 '08 at 20:44

shemnon

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And, in addition, to check if a map contains some not null value under a certain key, it is enough to check the following expression `if(aMap["aKey"]==aValue)`. – Naeel Maqsudov Dec 18 '17 at 12:58

score 69 · Answer 3 · edited Jul 27 '17 at 15:26

69

For lists, use contains:

[1,2,3].contains(1) == true

edited Jul 27 '17 at 15:26

Alex Gyoshev

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answered Sep 09 '08 at 13:58

banderson623

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Probably you wanted to say [1,2,3].contains(1). Because I am guessing contains function itself already returns a boolean. Why do you want to again compare it with a hardcoded 'true'. – Harshay Buradkar Nov 30 '12 at 03:01
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@HarshayBuradkar To make really sure `true == true`, of course #joke – Automatico Jan 20 '15 at 10:29

score 10 · Answer 4 · answered Jan 22 '20 at 06:30

10

You can use Membership operator:

def list = ['Grace','Rob','Emmy']
assert ('Emmy' in list)

Membership operator Groovy

answered Jan 22 '20 at 06:30

MagGGG

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score 8 · Answer 5 · answered Oct 02 '08 at 18:35

8

If you really want your includes method on an ArrayList, just add it:

ArrayList.metaClass.includes = { i -> i in delegate }

answered Oct 02 '08 at 18:35

John Flinchbaugh

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score 3 · Answer 6 · answered Dec 31 '14 at 18:20

IMPORTANT Gotcha for using .contains() on a Collection of Objects, such as Domains. If the Domain declaration contains a EqualsAndHashCode, or some other equals() implementation to determine if those Ojbects are equal, and you've set it like this...

import groovy.transform.EqualsAndHashCode
@EqualsAndHashCode(includes = "settingNameId, value")

then the .contains(myObjectToCompareTo) will evaluate the data in myObjectToCompareTo with the data for each Object instance in the Collection. So, if your equals method isn't up to snuff, as mine was not, you might see unexpected results.

score 2 · Answer 7 · edited Oct 08 '16 at 17:10

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def fruitBag = ["orange","banana","coconut"]
def fruit = fruitBag.collect{item -> item.contains('n')}

I did it like this so it works if someone is looking for it.

edited Oct 08 '16 at 17:10

Petter Friberg

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answered Oct 08 '16 at 16:41

HinataXV

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score 0 · Answer 8 · edited Jun 23 '20 at 19:19

0

You can also use matches with regular expression like this:

boolean bool = List.matches("(?i).*SOME STRING HERE.*")

edited Jun 23 '20 at 19:19

Pedro Fracassi

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answered Jun 23 '20 at 14:43

ninj

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How to check if element in groovy array/hash/collection/list?

8 Answers8