Variations in filter()
- If we want to filter using element index or position, we have to use filterIndexed().
- filterIndexed() function takes a predicate with two arguments: index and the value of an element.
- We can filter the collections by negative conditions by using filterNot().
Kotlin program of using the filterIndexed() and filterNot() functions –
Java
fun main(args: Array<String>) { val words = listOf("geek","for","geeks","all","world") //filtering a list by : words having length < 6 and index != 0 val filteredIndex = words.filterIndexed { index, s -> (index != 0) && (s.length < 6) } //filtering words having length >=3 using filterNot val filteredNot = words.filterNot { it.length <= 3 } println(filteredIndex) println(filteredNot)} |
Output:
[for, geeks, all, world] [geek, geeks, world]
Kotlin | Filtering Collections
In Kotlin, filtering is a prominent task of collection processing. The filtering conditions are defined by predicates – lambda functions that take a collection element and return true when the given element matches the predicate, and false means it doesn’t match the predicate.
- There are standard library contains number of functions that let you filter the collections in a single call.
- These functions don’t change the contents of the original collection or available for immutable and mutable both.
- We can assign it to a variable or chain the functions after filtering to operate the filtering result.