Class Set<E>

Adds the specified element to this set if it is not already present (optional operation). More formally, adds the specified element e to this set if the set contains no element e2 such that Objects.equals(e, e2). If this set already contains the element, the call leaves the set unchanged and returns false. In combination with the restriction on constructors, this ensures that sets never contain duplicate elements.

The stipulation above does not imply that sets must accept all elements; sets may refuse to add any particular element, including null, and throw an exception, as described in the specification for Collection#add Collection.add. Individual set implementations should clearly document any restrictions on the elements that they may contain.

Throws

UnsupportedOperationException if the add operation is not supported by this set

Throws

ClassCastException if the class of the specified element prevents it from being added to this set

Throws

NullPointerException if the specified element is null and this set does not permit null elements

Throws

IllegalArgumentException if some property of the specified element prevents it from being added to this set

Returns true if this set contains the specified element. More formally, returns true if and only if this set contains an element e such that Objects.equals(o, e).

Throws

ClassCastException if the type of the specified element is incompatible with this set (optional)

Throws

NullPointerException if the specified element is null and this set does not permit null elements (optional)

Returns true if this set contains no elements.

Returns an iterator over the elements in this set. The elements are returned in no particular order (unless this set is an instance of some class that provides a guarantee).

Returns the number of elements in this set (its cardinality). If this set contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.