HashSet class Methods in Java

java.util.HashSet

This class implements the Set interface, backed by a hash table. It makes no guarantees as to the iteration order of the set; in particular, it does not guarantee that the order will remain constant over time. This class permits the null element.

Some methods of HashSet class.

add(K): This method adds the specified element to this set if it is not already present.

addAll(Collection): This method adds all of the elements in the specified collection to this collection.

clear(): This method removes all of the elements from this set.

clone(): This method returns a shallow copy of this HashSet instance: the elements themselves are not cloned.

contains(Object): This method returns true if this set contains the specified element.

containsAll(Collection): This method returns true if this collection contains all of the elements in the specified collection.

equals(Object): This method compares the specified object with this set for equality.

forEach(Consumer): This method performs the given action for each element of the Iterable until all elements have been processed or the action throws an exception.

hashCode(): This method returns the hash code value for this set.

isEmpty(): This method returns true if this set contains no elements.

iterator(): This method returns an iterator over the elements in this set.

parallelStream(): This method returns a possibly parallel Stream with this collection as its source.

remove(Object): This method removes the specified element from this set if it is present.

removeAll(Collection): This method removes from this set all of its elements that are contained in the specified collection.

removeIf(Predicate): This method removes all of the elements of this collection that satisfy the given predicate.

retainAll(Collection): This method retains only the elements in this collection that are contained in the specified collection.

size(): This method returns the number of elements in this set (its cardinality).

spliterator(): This method creates a late-binding and fail-fast Spliterator over the elements in this set.

stream(): This method returns a sequential Stream with this collection as its source.

toArray(): This method returns an array containing all of the elements in this set.

toArray(IntFunction): This method returns an array containing all of the elements in this collection, using the provided generator function to allocate the returned array.

toArray(K[]): This method returns an array containing all of the elements in this set; the runtime type of the returned array is that of the specified array.

toString(): This method returns a string representation of this collection.