# retainAll method

void retainAll (Iterable<Object> elements)

Removes all elements of this set that are not elements in `elements`.

Checks for each element of `elements` whether there is an element in this set that is equal to it (according to `this.contains`), and if so, the equal element in this set is retained, and elements that are not equal to any element in `elements` are removed.

## Implementation

    void retainAll(Iterable<Object> elements);