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 class declaration

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

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

Methods of Java EnumSet class

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

Java EnumSet Example

1. import java.util.*;  
2. enum days {  
3.   SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY  
4. }  
5. public class EnumSetExample {  
6.   public static void main(String[] args) {  
7.     Set<days> set = EnumSet.of(days.TUESDAY, days.WEDNESDAY);  
8.     // Traversing elements  
9.     Iterator<days> iter = set.iterator();  
10.     while (iter.hasNext())  
11.       System.out.println(iter.next());  
12.   }  
13. }  

Output:

TUESDAY
WEDNESDAY

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Java EnumSet Example: allOf() and noneOf()

1. import java.util.*;  
2. enum days {  
3.   SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY  
4. }  
5. public class EnumSetExample {  
6.   public static void main(String[] args) {  
7.     Set<days> set1 = EnumSet.allOf(days.class);  
8.       System.out.println("Week Days:"+set1);  
9.       Set<days> set2 = EnumSet.noneOf(days.class);  
10.       System.out.println("Week Days:"+set2);     
11.   }  
12. }  

Output:

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