lastOrNull

LastOrNull is a Kotlin standard library function that returns the last element of an iterable or a sequence, or null if the collection is empty. It is available as an extension on Iterable<T> and Sequence<T>, and there is an overload that accepts a predicate. This makes it the null-safe counterpart to last, which throws an exception when no element is found.

Without a predicate, lastOrNull traverses the collection or sequence to obtain its last element. For lists with efficient random access, implementations may optimize, but for sequences it must process elements in order until the end. If the collection has no elements, the function returns null. With a predicate, lastOrNull returns the last element that satisfies the predicate, or null if none do.

Return type and null safety: the function returns a value of type T? (nullable). This supports safe calls and the Elvis operator, for example: list.lastOrNull() ?: defaultValue or list.lastOrNull()?.let { … }.

Examples:

- val nums = listOf(1, 2, 3)

nums.lastOrNull() // 3

nums.lastOrNull { it > 2 } // 3

- val empty = emptyList<Int>()

empty.lastOrNull() // null

Comparison with last:

- last() returns the last element but throws NoSuchElementException if the collection is empty.

- lastOrNull() returns null instead of throwing, optionally applying a predicate to filter candidates.

See also: firstOrNull, first, last, lastOrNull with a predicate.