Kotlin List plus()
Syntax & Examples

Syntax of List.plus()

There are 4 variations for the syntax of List.plus() extension function. They are:

operator fun <T> Iterable<T>.plus(element: T): List<T>

This extension function returns a list containing all elements of the original collection and then the given element.

operator fun <T> Iterable<T>.plus( elements: Array<out T> ): List<T>

This extension function returns a list containing all elements of the original collection and then all elements of the given elements array.

operator fun <T> Iterable<T>.plus( elements: Iterable<T> ): List<T>

This extension function returns a list containing all elements of the original collection and then all elements of the given elements collection.

operator fun <T> Iterable<T>.plus( elements: Sequence<T> ): List<T>

This extension function returns a list containing all elements of the original collection and then all elements of the given elements sequence.

✐ Examples

1 Example

In this example,

We create a list named list1 containing the integers [1, 2, 3].
We use the plus() function to append the integer 4 to list1.
Finally, we print the resulting list to standard output using the println function.

Kotlin Program

fun main(args: Array<String>) {
    val list1 = listOf(1, 2, 3);
    val result = list1.plus(4);
    println(result);
}

Output

[1, 2, 3, 4]

2 Example

In this example,

We create a list named list1 containing the characters ['a', 'b', 'c'].
We use the plus() function to append the elements 'd' and 'e' from an array to list1.
Finally, we print the resulting list to standard output using the println function.

Kotlin Program

fun main(args: Array<String>) {
    val list1 = listOf('a', 'b', 'c');
    val result = list1.plus(arrayOf('d', 'e'));
    println(result);
}

Output

[a, b, c, d, e]

3 Example

In this example,

We create a list named list1 containing the strings ['apple', 'banana'].
We use the plus() function to append the strings 'orange' and 'grape' from another list to list1.
Finally, we print the resulting list to standard output using the println function.

Kotlin Program

fun main(args: Array<String>) {
    val list1 = listOf("apple", "banana");
    val result = list1.plus(listOf("orange", "grape"));
    println(result);
}

Output

[apple, banana, orange, grape]

4 Example

In this example,

We create a list named list1 containing the integers [1, 2, 3].
We use the plus() function to append the integers 4, 5, 6 from a sequence to list1.
Finally, we print the resulting list to standard output using the println function.

Kotlin Program

fun main(args: Array<String>) {
    val list1 = listOf(1, 2, 3);
    val result = list1.plus(sequenceOf(4, 5, 6));
    println(result);
}

Output

[1, 2, 3, 4, 5, 6]

Summary

In this Kotlin tutorial, we learned about plus() extension function of List: the syntax and few working examples with output and detailed explanation for each example.