What is EnumSet in Java?
- The EnumSet is a specialized implementation of the Set interface designed for use with enumeration types.
- It derives from the AbstractSet class and implements the Set interface.
- Enum sets are internally represented as bit vectors. This is a very compact and efficient representation.
- This class’s space and time performance should be sufficient to allow it to be used as a high-quality, typesafe alternative to traditional int-based “bit flags.” Even bulk operations (such as containsAll and retainAll) should be very fast if their argument is also an enum set.
Syntax:
public abstract class EnumSet<E extends Enum<E>> where E specifies the elements.
Methods of EnumSet Class:
| Method | Description |
|---|---|
| allOf(Class<E> elementType) | Creates an enum set that contains all elements of the specified element type. |
| clone() | Returns a copy of this set. |
| complementOf(EnumSet<E> s) | Creates an enum set with the same element type as the specified set, initially containing all elements of this type that are not in the specified set. |
| copyOf(Collection<E> c) | Generates an enum set from the specified collection. |
| copyOf(EnumSet<E> s) | Creates an enum set with the same element type as the specified enum set, with the same elements at first (if any). |
| noneOf(Class<E> elementType) | This method generates an empty enum set with the specified element type. |
| of(E e) | Creates an enum set with the specified element as the first element. |
| range(E from, E to) | Creates an enum set with all of the elements in the range defined by the two endpoints specified. |
Example:
import java.util.EnumSet;
// Enum
enum Week { SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY,FRIDAY,SATURDAY };
// Main class
public class COderz {
// Main driver method
public static void main(String[] args) {
// Creating a set
EnumSet<Week> set1, set2, set3, set4;
// Adding elements
set1 = EnumSet.of(Week.SATURDAY, Week.MONDAY,
Week.FRIDAY, Week.SUNDAY);
set2 = EnumSet.complementOf(set1);
set3 = EnumSet.allOf(Week.class);
set4 = EnumSet.range(Week.WEDNESDAY, Week.SATURDAY);
// Printing corresponding elements in Sets
System.out.println("Set 1: " + set1);
System.out.println("Set 2: " + set2);
System.out.println("Set 3: " + set3);
System.out.println("Set 4: " + set4);
}
}
Output:
Set 1: [SUNDAY, MONDAY, FRIDAY, SATURDAY]
Set 2: [TUESDAY, WEDNESDAY, THURSDAY]
Set 3: [SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY]
Set 4: [WEDNESDAY, THURSDAY, FRIDAY, SATURDAY]Note: also read about the AbstractSet in Java
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Staying up to the mark is what defines me. Hi all! I’m Rabecca Fatima a keen learner, great enthusiast, ready to take new challenges as stepping stones towards flying colors.
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Commented on September 14, 2022 at 10:36 am