Set: EnumSet is a specialized implementation of Set.

1. Use: It is mainly used with enum types.

2. Single enum type: All the elements in an EnumSet must

come from a single enum type when the set is created.

3. Bit vector: Internally, EnumSet is represented as bit

vector.

4. Iterator: The iterator of EnumSet traverses the elements in

their natural order. (It is the order in which the enum

constants are declared).

5. Null: In an EnumSet, null elements are not permitted. If we

try to insert a null element it throws NullPointerException.

6. Thread-safe: EnumSet is not a synchronized collection.

For use in multi-threading scenarios, EnumSet should be

synchronized.

7. Bit flags: EnumSet is a very good alternative to int based

“bit flags” implementation

https://www.geeksforgeeks.org/enumset-class-java/