Java EnumSet noneOf() Method

The EnumSet.noneOf() method is a part of java.util package. This method is used to create an empty EnumSet for a given enum type. Suppose we create a set with no elements first, but that will only hold the enum constants of a particular enum class. In this article, we are going to learn about the EnumSet noneOf() method in Java.

Syntax of EnumSet noneOf() Method

public static <E extends Enum<E>> EnumSet<E> noneOf(Class<E> elementType)

• Parameters: This method accepts one parameter, elementType of element type which refers to the class object of the element type for this enum set. 
• Return Value: This method does not return any value. 
• Exceptions: This method throws a NullPointerException if the elementType is Null.

This method creates an empty EnumSet. This can hold enum constants of the given enum type, but starts with no elements. This is useful when we want to start with an empty set and add elements later.

Examples of Java EnumSet noneOf() Method

Example 1: In this example, we will create an empty EnumSet using the method noneOf().

// Java program to demonstrate 
// EnumSet.noneOf() method usage
import java.util.*;

// Define an enum type
enum GFG {
    Welcome, To, The, World, of, Geeks
}

public class Geeks {
    public static void main(String[] args) {
        
        // Create an EnumSet that contains 
        // all constants of GFG
        EnumSet<GFG> allSet = EnumSet.allOf(GFG.class);
        System.out.println("All elements: " + allSet);

        // Create an empty EnumSet of 
        // type GFG using noneOf()
        EnumSet<GFG> emptySet = EnumSet.noneOf(GFG.class);
        System.out.println("Empty set: " + emptySet);
    }
}

Example 2: In this example, we will use the noneOf() method with a different enum.

// Java program to demonstrate EnumSet.noneOf() 
// method with a different enum
import java.util.*;

// Define another enum type
enum CARS {
    
    RANGE_ROVER, MUSTANG, CAMARO, AUDI, BMW
}

public class Geeks {
    public static void main(String[] args) {
        
        // Create an EnumSet with all 
        // CARS enum constants
        EnumSet<CARS> allCars = EnumSet.allOf(CARS.class);
        System.out.println("All cars: " + allCars);

        // Create an empty EnumSet of type CARS
        EnumSet<CARS> emptyCarsSet 
        = EnumSet.noneOf(CARS.class);
        System.out.println("Empty cars set: " 
        + emptyCarsSet);
    }
}

Important Points:

• This method is type-safe, so that we can only add enum constants of that type.
• This method is very useful when we want to initialize an empty set and add enum values later.

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Article Tags :

• Java
• java-EnumSet

Practice Tags :

• Java