Kotlin - Idiomatic way to check array contains value

Question

What's an idiomatic way to check if an array of strings contains a value in Kotlin? Just like ruby's #include?.

I thought about:

array.filter { it == "value" }.any()

Is there a better way?

Geoffrey Marizy · Accepted Answer · 2022-09-03T19:35:28.707

163

The equivalent you are looking for is the contains operator.

array.contains("value")

Kotlin offer an alternative infix notation for this operator:

"value" in array

It's the same function called behind the scene, but since infix notation isn't found in Java we could say that in is the most idiomatic way.

edited Sep 03 '22 at 19:35

answered Feb 14 '17 at 19:43

Geoffrey Marizy

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When I try this in Kotlin I get a "Type inference failed. The value of the type parameter T should be mentioned in the input Types." private var domainsArray = arrayOf("@ebay.com", "@google.com", "@gmail.com", "@umd.edu") var domainFound = Arrays.asList(domainsArray).contains(email) – AdamHurwitz Aug 03 '17 at 01:30
Just write var domainFound = domainsArray.contains(email) or more idiomatic var domainFound = email in domainsArray – Geoffrey Marizy Aug 03 '17 at 13:49
Any idea how to compare with ignorecase string? array.contains("value") do not check ignorecase for string. – Viks Oct 20 '21 at 01:12
You could map array with the toLowerCase String extension function before calling contains. – Geoffrey Marizy Oct 24 '21 at 17:01

score 135 · Answer 2 · answered Jul 03 '18 at 05:50

135

You could also check if the array contains an object with some specific field to compare with using any()

listOfObjects.any{ object -> object.fieldxyz == value_to_compare_here }

answered Jul 03 '18 at 05:50

Amar Jain

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score 44 · Answer 3 · answered Aug 27 '19 at 21:17

44

Here is code where you can find specific field in ArrayList with objects. The answer of Amar Jain helped me:

listOfObjects.any{ it.field == "value"}

answered Aug 27 '19 at 21:17

Dimitar

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Gerson · Answer 4 · 2017-02-14T20:20:53.833

39

Using in operator is an idiomatic way to do that.

val contains = "a" in arrayOf("a", "b", "c")

edited Feb 14 '17 at 20:20

answered Feb 14 '17 at 19:57

Gerson

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score 24 · Answer 5 · answered Feb 14 '17 at 19:59

24

You can use the in operator which, in this case, calls contains:

"value" in array

answered Feb 14 '17 at 19:59

mfulton26

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score 10 · Answer 6 · answered Nov 18 '19 at 06:30

You can use it..contains(" ")

 data class Animal (val name:String)


 val animals = listOf(Animal("Lion"), Animal("Elephant"), Animal("Tiger"))

 println(animals.filter { it.name.contains("n") }.toString())

output will be

[Animal(name=Lion), Animal(name=Elephant)]

score 7 · Answer 7 · answered Aug 10 '20 at 19:13

7

You can use find method, that returns the first element matching the given [predicate], or null if no such element was found. Try this code to find value in array of objects

 val findedElement = array?.find {
            it.id == value.id
 }
 if (findedElement != null) {
 //your code here           
 }

answered Aug 10 '20 at 19:13

L.Petrosyan

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How can you get the position of findedElement value from array? – Aan Oct 26 '21 at 13:23
@AnzyShQ you can find a position with a methods `array.indexIf(Object o)` -> will return you index of first founded element, `array.lastIndexOf(Object o)` -> will return you index of last founded element. You can also use predicate too, etc `array.indexOfLast { it.name == "test " }` or `array.indexOfFirst { it.name == "test "}` – L.Petrosyan Oct 27 '21 at 13:10

Kotlin - Idiomatic way to check array contains value

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