Returns {@code true} if this set contains the specified element.
More formally, returns {@code true} if and only if this set
contains an element {@code e} such that
<tt>(o==null ? e==null : o.equals(e))</tt>.
@param o object to be checked for containment in this set
@return {@code true} if this set contains the specified element
@throws ClassCastException if the specified object cannot be compared
with the elements currently in the set
@throws NullPointerException if the specified element is null
and this set uses natural ordering, or its comparator
does not permit null elements
Returns {@code true} if this set contains the specified element. More formally, returns {@code true} if and only if this set contains an element {@code e} such that <tt>(o==null ? e==null : o.equals(e))</tt>.
@param o object to be checked for containment in this set @return {@code true} if this set contains the specified element @throws ClassCastException if the specified object cannot be compared with the elements currently in the set @throws NullPointerException if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements