LinkedHashSet

LinkedHashSet is a subclass of HashSet in Java that maintains the insertion order of the elements. It extends the HashSet class and implements the Set interface. It is similar to HashSet in terms of storing unique elements but maintains the order in which the elements were inserted.

LinkedHashSet uses a combination of a hash table and a linked list to maintain the elements in the order in which they were inserted. It provides constant time performance for the basic operations such as add, remove, contains, and size.

One of the main advantages of LinkedHashSet over HashSet is that it can be used in scenarios where the order of the elements is important. For example, in a web application, a LinkedHashSet can be used to store the order of the pages that a user has visited.

LinkedHashSet is not synchronized, so it is not thread-safe. However, it can be synchronized using the Collections.synchronizedSet() method to make it thread-safe.

Overall, LinkedHashSet is a useful class in Java that provides the benefits of HashSet along with maintaining the order of the elements.