lookup method

Optional<T> lookup(
  1. Object? element
)

Returns an Optional containing an element equal to element if there is one in this set, otherwise returns Optional.empty.

Checks whether element is in the set, like contains, and if so, returns the object in the set wrapped in an Optional, otherwise returns Optional.empty.

This lookup can not distinguish between an object not being in the set or being the null value. The method contains can be used if the distinction is important.

Implementation

Optional<T> lookup(Object? element) =>
    Optional.ofNullable(_set.lookup(element));