Returns the position of a value, or -1 if the value is not found.

Returns the position of the first of equivalent values. Equivalence is defined by the equality operator intrinsic to the collection, either the one given as the equals argument to its constructor, or Object.equals by default.

For a SortedSet, this operation is fast, because it is backed by a binary search tree. For a SortedArray, or SortedArraySet, this is also fast, employing a binary search.

The implementation of indexOf for Array, List, and Deque is slower but more flexible.

On collections


  • indexOf(value)