Java CopyOnWriteArraySet class
CopyOnWriteArraySet is a thread-safe Set in Java. It ensures safe concurrent access by creating a new copy of the internal array for each modification.
Java TreeSet class
Java TreeSet class extends AbstractSet and implements NavigableSet interface. It is very similar to HashSet class, except it stores the element in sorted order.
Java LinkedHashSet class
Java LinkedHashSet class extends HashSet and implements Set interface. It is very very similar to HashSet class, except if offers the predictable iteration order.
Java HashSet class
Java HashSet class implements the Set interface, backed by a hash table(actually a HashMap instance). If does not offer any guarantees as to the iteration order, and allows null element.
Convert Set to List in Java and Vice-versa
Learn to convert a Set to List in Java using constructor, addAll() and Java 8 streams. Learn to convert list to set to remove duplicates.