What are the differences between LinkedHashSet and HashSet data structures in Java?

The main difference between LinkedHashSet and HashSet in Java lies in the order of element storage and performance:

• HashSet — implements a set based on a hash table. Elements do not have a specific order when iterated over. The main advantage is high speed of add, remove, and search operations.

• LinkedHashSet — extends HashSet but additionally maintains a linked list that preserves the insertion order of elements. When iterated, elements are returned in the order they were added.

Example:

HashSet<String> hashSet = new HashSet<>();
hashSet.add("apple");
hashSet.add("banana");
hashSet.add("cherry");

LinkedHashSet<String> linkedHashSet = new LinkedHashSet<>();
linkedHashSet.add("apple");
linkedHashSet.add("banana");
linkedHashSet.add("cherry");

System.out.println(hashSet); // Order may be arbitrary
System.out.println(linkedHashSet); // Will output [apple, banana, cherry]

Summary:

• Use HashSet if order does not matter and maximum performance is needed.
• Use LinkedHashSet if the insertion order of elements is important.