Methods of Set

The Set interface includes all the methods of the Collection interface. It’s because Collection is a super interface of Set. Some of the commonly used methods of the Collection interface that’s also available in the Set interface are:

1. add() - adds the specified element to the set.
2. addAll() - adds all the elements of the specified collection to the set.
3. iterator() - returns an iterator that can be used to access elements of the set sequentially.
4. remove() - removes the specified element from the set.
5. removeAll() - removes all the elements from the set that is present in another specified set.
6. retainAll() - retains all the elements in the set that are also present in another specified set.
7. clear() - removes all the elements from the set.
8. size() - returns the length (number of elements) of the set.
9. toArray() - returns an array containing all the elements of the set.
10. contains() - returns true if the set contains the specified element.
11. containsAll() - returns true if the set contains all the elements of the specified collection.
12. hashCode() - returns a hash code value (address of the element in the set).

The Java Set interface allows us to perform basic mathematical set operations like union, intersection, and subset.

1. Union - to get the union of two sets x and y, we can use x.addAll(y)
2. Intersection - to get the intersection of two sets x and y, we can use x.retainAll(y)
3. Subset - to check if x is a subset of y, we can use y.containsAll(x).