Kotlin List.find() – Examples

Kotlin List.find()

The List.find() function in Kotlin is used to find the first element in a list that satisfies a given predicate(condition).

Syntax

The syntax of List.find() function is

fun <T> Iterable<T>.find(predicate: (T) -> Boolean): T?

where

Parameter	Description
predicate	A function that takes an element and returns true if the element satisfies the desired condition.

where T is the type of elements in the list.

The function takes a predicate as an argument and returns the first element that satisfies the given predicate. If no such element is found, it returns null.

Example 1: Basic Usage of List.find()

In this example, we shall take a list of integer values in numbers, and find the first even number in this list, using List.find() with the predicate that the value is even number.

Kotlin Program

fun main() {
    val numbers = listOf(1, 3, 5, 8, 7, 10)
    val firstEven = numbers.find { it % 2 == 0 }

    println(firstEven)
}

Output

8

Example 2: Finding a Specific Object using List.find()

In this example, we take a list of user defined objects of type Person. Using List.find() function, we have to get the first Person object whose age property is greater than 25.

Kotlin Program

data class Person(val name: String, val age: Int)

val people = listOf(
    Person("Ram", 22),
    Person("Kiran", 30),
    Person("Veena", 25)
)

val firstPerson = people.find { it.age > 25 }

println(firstPerson)

Output

Person(name=Kiran, age=30)

Example 3: List.find() where the predicate finds no element

In this example, we shall take a list of integer values in numbers, and find the first negative number in this list, using List.find(). We shall take the values in the numbers list, such that there is no negative element.

Kotlin Program

fun main() {
    val numbers = listOf(1, 3, 5, 7, 9)
    val firstNegative = numbers.find { it < 0 }

    println(firstNegative)
}

Output

null

Summary

In this tutorial, we have learnt about List.find() function, its syntax, and usage, with well detailed examples.