Join Two Lists in Kotlin

In Kotlin, there are multiple ways to join lists.

1. Using Plus Operator

A simple solution to join two lists is with the plus operator.

import java.util.Arrays

fun <T> merge(first: List<T>, second: List<T>): List<T> {
    return first + second
}
 
fun main() {
    val fruits = listOf("Apple", "Banana")
    val vegetables = listOf("Tomato", "Cucumber")
 
    var list: List<String>? = merge(fruits, vegetables)
 
    println(list)       
}

Output

[Apple, Banana, Tomato, Cucumber]

2. Using plus() function

Another way we can join lists is to use plus() function.

import java.util.Arrays

fun <T> merge(first: List<T>, second: List<T>): List<T> {
    return first.plus(second)
}
 
fun main() {
    val fruits = listOf("Apple", "Banana")
    val vegetables = listOf("Tomato", "Cucumber")
 
    var list: List<String>? = merge(fruits, vegetables)
 
    println(list)       
}

Output

[Apple, Banana, Tomato, Cucumber]

3. Using addAll() function

Another way we can join lists is to use addAll() function.

import java.util.Arrays

fun <T> merge(first: List<T>, second: List<T>): List<T> {
    val list: MutableList<T> = ArrayList()
    list.addAll(first)
    list.addAll(second)
    return list
}
 
fun main() {
    val fruits = listOf("Apple", "Banana")
    val vegetables = listOf("Tomato", "Cucumber")
 
    var list: List<String>? = merge(fruits, vegetables)
 
    println(list)       
}

Output

[Apple, Banana, Tomato, Cucumber]

Conclusion

In this page (written and validated by A. Gawali) you learned about Join Two Lists in Kotlin . What's Next? If you are interested in completing Kotlin tutorial, we encourage you simply to start here: Kotlin Tutorial.

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