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Java EnumSet: How to use EnumSet in Java?

Last updated on Nov 27,2019 210 Views
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Java is one of the most popular programming languages used to build a wide variety of applications. While building applications, we often use enumerations to serve a group of named constants. But, if you want to implement a Set interface with the enumeration type, then you have to use the EnumSet in Java. In this article on Java EnumSet, I will be covering the following topics:

Java Logo - Java EnumSet - Edureka

What is Java EnumSet?

EnumSet is an implementation of the Set collections to work with the enum type. EnumSet extends from the AbstractSet and implements the Set interface. The following are a few important points you need to understand about EnumSet in Java:

  • Contains only enum values which belong to the same enumeration type
  • It is a member of the Java collections framework
  • Provides high performance set implementation and is not synchronized
  • It does not allow the user to add NULL values and throws a NullPointerException
  • Elements are stored in the order of which they are saved
  • Uses a fail-safe iteration, which can be used to make sure that ConcurrentModificationException is thrown

You can declare Java EnumSet in the following manner:

Declaration

public abstract class EnumSet<E extends Enum<E>> 

Next, in this article on Java EnumSet, let us understand the different methods offered by this class.

Methods of EnumSet

The various methods offered by Java EnumSet are as follows:

MethodModifier and TypeDescription
of(E e1)static <E extends Enum<E>> 
EnumSet<E>
Used to create an enum set initially containing the mentioned element i.e. e1.
of(E e1, E e2)static <E extends Enum<E>> 
EnumSet<E>
Used to create an enum set initially containing the mentioned elements. Here, it is e1, e2.
range(E from, E to)static <E extends Enum<E>> 
EnumSet<E>
Used to create an enum set initially containing all of the elements in the range defined by the two mentioned endpoints.
allOf(Class<E> elementType)static <E extends Enum<E>> 
EnumSet<E>
Used to create an enum set containing all of the elements in the menioned element type.
copyOf(Collection<E> c)static <E extends Enum<E>> 
EnumSet<E>
Used to create an enum set initialized from the mentioned collection.
copyOf(EnumSet<E> s)static <E extends Enum<E>> 
EnumSet<E>
Used to create an enum set with the same element type as the mentioned enum set, initially containing the same elements (if there any present).
complementOf(EnumSet<E> s)static <E extends Enum<E>> 
EnumSet<E>
Used to create an enum set with the same element type as the mentioned enum set, initially containing all the elements of this type that are not contained in the specified set.
noneOf(Class<E> elementType)static <E extends Enum<E>> 
EnumSet<E>
Used tp create an empty enum set with the specified element type.
clone()EnumSet<E>Used to return a copy of this set.

Note: You can use the of() method up to 5 parameters. So, you can create an enum set initially containing the specified elements as follows:

  • of(E e1, E e2, E e3)
  • of(E e1, E e2, E e3, E e4)
  • of(E e1, E e2, E e3, E e4, E e5)

Since, I have discussed the methods used with EnumSet, next in Java EnumSet tutorial, let us see the practical operations of these methods.

Operations of Java EnumSet

To explain you the operations of EnumSet, I will consider the following code snippet. This code snippet contains a set of enum values [DevOps, Big Data, Python, Data Science, RPA]. In the later section of the code, I will show you how to use different methods in the following sequence:

  • of(E e1)
  • of(E e1, E e2)
  • of(E e1, E e2, E e3)
  • of(E e1, E e2, E e3, E e4)
  • of(E e1, E e2, E e3, E e4, E e5)
  • range(E from, E to)
  • allOf(Class<E> elementType)
  • copyOf(Collection<E> c)
  • copyOf(EnumSet<E> s)
  • complementOf(EnumSet<E> s)
  • noneOf(Class<E> elementType)
  • clone()

Code Snippet:

package edureka;
import java.util.ArrayList;
import java.util.Collection;
import java.util.EnumSet; 
enum Courses 
{ 
	DevOps, BigData, Python, DataScience, RPA
}; 
public class Example {
	    public static void main(String[] args)  
	    { 
	    	// Create an EnumSet 
	        EnumSet<Courses> sample_set;  
	        
	        //of method
	        // Add single element
	        sample_set = EnumSet.of(Courses.DevOps); 
	        // Display the set 
	        System.out.println("The EnumSet after adding a single element is: " + sample_set); 
	        
	        // Add two elements
	        sample_set = EnumSet.of(Courses.DevOps, Courses.BigData); 
	        // Display the set 
	        System.out.println("The EnumSet after adding two elements is: " + sample_set); 
	        
	        // Add three elements
	         sample_set = EnumSet.of(Courses.DevOps, Courses.BigData, Courses.Python); 
	        // Display the set 
	        System.out.println("The EnumSet after adding three elements is: " + sample_set); 
	        
	        // Add four elements
	         sample_set = EnumSet.of(Courses.DevOps, Courses.BigData, Courses.Python, Courses.DataScience); 
	        // Display the set 
	        System.out.println("The EnumSet after adding four elements is: " + sample_set); 
	        
	        // Add five elements
	         sample_set = EnumSet.of(Courses.DevOps, Courses.BigData, Courses.Python, Courses.DataScience,Courses.RPA); 
	        // Display the set 
	        System.out.println("The EnumSet after adding five elements is: " + sample_set); 
	        
	        //Range method
	        sample_set = EnumSet.range(Courses.BigData, Courses.DataScience); 
	        // Display the set 
	        System.out.println("The range of the EnumSet is: " + sample_set); 
	        
	        //allOf method
	        sample_set = EnumSet.allOf(Courses.class); 
	        // Display the set 
	        System.out.println("All the elements in the EnumSet are: " + sample_set); 
	        
	        //copyOf(Collection) method
	        
	        // Create an empty collection 
	        Collection<Courses> samplecollection = new ArrayList<Courses>();	        
	        // Add elements to the samplecollection 
	        samplecollection.add(Courses.DevOps); 
	        samplecollection.add(Courses.BigData); 
	        samplecollection.add(Courses.Python); 	        
	        // Display the sample collection set 
	        System.out.println("Elements in the sample collection set are: " + samplecollection); 	        
	        //Create a new EnumSet to store the collection items
	        EnumSet<Courses> final_enumset = EnumSet.copyOf(samplecollection);
	        // Display the EnumSet 
	        System.out.println("Elements in the EnumSet are: " + final_enumset); 
	        
	        //copyOf(EnumSet) method
	        
	        // Get all the elements from Courses  
	        EnumSet<Courses> example_set = EnumSet.allOf(Courses.class);
	        // Display the initial EnumSet(sample_set) 
	        System.out.println("The elements in the initial EnumSet are: " + example_set); 
	        // Copy the elements from the above set
	        EnumSet<Courses> final_set = EnumSet.copyOf(example_set);
	        // Display the elements in the copied EnumSet 
	        System.out.println("The elements in the copied EnumSet are: " + final_set); 
	     
	        //complementOf method
	        //Sample Set
	        sample_set = EnumSet.of(Courses.DevOps, Courses.BigData, Courses.Python);
	        //Create an EnumSet
	        EnumSet<Courses> complement_set;
	        //Complement the above set
	        complement_set = EnumSet.complementOf(sample_set);
	        // Display the elements in the complement EnumSet 
	        System.out.println("The elements in the complement EnumSet are: " + complement_set); 
	 
	        //noneOf method
	        // Create empty set 
	        EnumSet<Courses> none_example_set = EnumSet.noneOf(Courses.class); 
	        // Display the elements in the set 
	        System.out.println("EnumSet consists of the elements: " + none_example_set); 
	    
	        //clone method
	        EnumSet<Courses> final_clone_set = sample_set.clone(); 
	        //Display the EnumSet
	        System.out.println("The clone set consists of the elements:" + final_clone_set);	    
	    
	    } 
}

Output:

The EnumSet after adding a single element is: [DevOps]
The EnumSet after adding two elements is: [DevOps, BigData]
The EnumSet after adding three elements is: [DevOps, BigData, Python]
The EnumSet after adding four elements is: [DevOps, BigData, Python, DataScience]
The EnumSet after adding five elements is: [DevOps, BigData, Python, DataScience, RPA]
The range of the EnumSet is: [BigData, Python, DataScience]
All the elements in the EnumSet are: [DevOps, BigData, Python, DataScience, RPA]
Elements in the sample collection set are: [DevOps, BigData, Python]
Elements in the EnumSet are: [DevOps, BigData, Python]
The elements in the initial EnumSet are: [DevOps, BigData, Python, DataScience, RPA]
The elements in the copied EnumSet are: [DevOps, BigData, Python, DataScience, RPA]
The elements in the complement EnumSet are: [DataScience, RPA]
EnumSet consists of the elements: []
The clone set consists of the elements:[DevOps, BigData, Python]

This brings us to the end of this article on Java EnumSet. If you want to know more about Java you can refer to our other Java Blogs.

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