EnumSet in Java

In Java, the EnumSet is a specialized set implementation for use with enum types. It is a part of java.util package and provides a highly optimized set for storing enum constants. The EnumSet is one of the specialized implementations of the Set interface for use with the enumeration type.

• It extends the AbstractSet class and implements the Set Interface in Java.
• The EnumSet class is a member of the Java Collections Framework and is not synchronized.
• It’s a high-performance set implementation, much faster than HashSet.
• All of the elements in an EnumSet must come from a single enumeration type that is specified when the set is created either explicitly or implicitly.
• It does not allow null Objects and throws NullPointerException if we do so.
• It uses a fail-safe iterator, so it won’t throw ConcurrentModificationException if the collection is modified while iterating.

Example: This example demonstrates how to create an EnumSet and print its elements

// Creating an EnumSet
import java.util.EnumSet;

enum Student { Geek1, Geek2, Geek3, Geek4, Geek5 }

public class Geeks {
    public static void main(String[] args) {
        
        // Create an EnumSet containing specific elements
        EnumSet<Student> e = EnumSet.of(Student.Geek1, Student.Geek2, Student.Geek3);

        System.out.println("EnumSet: " + e);
    }
}

EnumSet: [Geek1, Geek2, Geek3]

Hierarchy of EnumSet

The Hierarchy of EnumSet is as follows: