How to remove duplicates from an Array<String?> in kotlin?
Use the distinct extension function:
val a = arrayOf("a", "a", "b", "c", "c")
val b = a.distinct() // ["a", "b", "c"]
There's also distinctBy function that allows one to specify how to distinguish the items:
val a = listOf("a", "b", "ab", "ba", "abc")
val b = a.distinctBy { it.length } // ["a", "ab", "abc"]
As @mfulton26 suggested, you can also use toSet, toMutableSet and, if you don't need the original ordering to be preserved, toHashSet. These functions produce a Set instead of a List and should be a little bit more efficient than distinct.
You may find useful:
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toSetortoMutableSetwhich have less overhead thandistinctand if ordering does not matter you can usetoHashSet.to*Setis more efficient (space & time) thandistinct[By]because it returns theSetdirectly instead of using aSetinternally and converting it to aListas its return value and 2)distinctByis can be more efficient thandistinctsimply because you can avoid full object equality comparison. Both are valid points. I ran with your statement that "certainly it doesn't always have overhead" and I was replying to that and overlooked that you were comparingdistinctwithdistinctBy(and not withto*Set).Iterable.distinctactually doestoMutableSet().toList()internally. So don't worry about performance :-)