Java: EnumSet Class


Java EnumSet class is the specialized Set implementation for use with enum types. It inherits AbstractSet class and implements the Set interface.

EnumSet class hierarchy

The hierarchy of EnumSet class is given in the figure given below.
EnumSet

EnumSet class declaration

Let’s see the declaration for java.util.EnumSet class.

public abstract class EnumSet<E extends Enum> extends AbstractSet implements Cloneable, Serializable  

Methods of Java EnumSet Class

Method Description
static <E extends Enum> EnumSet allOf(Class elementType) It is used to create an enum set containing all of the elements in the specified element type.
static <E extends Enum> EnumSet copyOf(Collection c) It is used to create an enum set initialized from the specified collection.
static <E extends Enum> EnumSet noneOf(Class elementType) It is used to create an empty enum set with the specified element type.
static <E extends Enum> EnumSet of(E e) It is used to create an enum set initially containing the specified element.
static <E extends Enum> EnumSet range(E from, E to) It is used to create an enum set initially containing the specified elements.
EnumSet clone() It is used to return a copy of this set.

Example :EnumSet

import java.util.*;
enum days {
  SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY
}
public class EnumSetExample {
  public static void main(String[] args) {
    Set set = EnumSet.of(days.TUESDAY, days.WEDNESDAY);
    // Traversing elements
    Iterator iter = set.iterator();
    while (iter.hasNext())
      System.out.println(iter.next());
  }
}

Output :


TUESDAY
WEDNESDAY

Java EnumSet Example: allOf() and noneOf()

import java.util.*;
enum days {
  SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY
}
public class EnumSetExample {
  public static void main(String[] args) {
    Set set1 = EnumSet.allOf(days.class);
      System.out.println("Week Days:"+set1);
      Set set2 = EnumSet.noneOf(days.class);
      System.out.println("Week Days:"+set2);
  }
}

Output :


Week Days:[SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY]
Week Days:[]

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