Adds the specified element to this set if it is not already present.
More formally, adds the specified element {@code e} to this set if
this set contains no element {@code e2} such that
{@code Objects.equals(e, e2)}.
If this set already contains the element, the call leaves the set
unchanged and returns {@code false}.
@param e element to be added to this set
@return {@code true} if this set did not already contain the specified
element
Adds the specified element to this set if it is not already present. More formally, adds the specified element {@code e} to this set if this set contains no element {@code e2} such that {@code Objects.equals(e, e2)}. If this set already contains the element, the call leaves the set unchanged and returns {@code false}.
@param e element to be added to this set @return {@code true} if this set did not already contain the specified element