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EnumSet copyOf() Method in Java

Last Updated : 02 Jul, 2018
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  1. The java.util.EnumSet.copyOf(Collection collect) method in Java is used to copy all of the contents from a collection to a new enum set. At first, the collection is made out of the elements of the enum and then a new enum set is created, which is the copy of the collection.

    Syntax:

    New_Enum_Set = EnumSet.copyOf(Collection collect)

    Parameters: The method accepts one parameter collect of the object type of the enum and refers to the collection whose values are to be copied into the New_Enum_Set.

    Return Values: The method does not return any values.

    Exceptions:

    • IllegalArgumentException : This exception is thrown if collect is not an EnumSet instance and contains elements that cannot be compared with the enum or contains no element.
    • NullPointerException : This exception is thrown if collect is NULL.

    Below program illustrates the working of java.util.EnumSet.copyOf() method:




    // Java program to demonstrate copyOf() method
    import java.util.*;
      
    // Creating an enum of GFG type
    enum GFG {
        Welcome,
        To,
        The,
        World,
        of,
        Geeks
    }
    ;
      
    public class Enum_Set_Demo {
      
        public static void main(String[] args)
        {
      
            // Creating an empty collection
            Collection<GFG> collect = new ArrayList<GFG>();
      
            // Adding elements to the Collection
            collect.add(GFG.Welcome);
            collect.add(GFG.World);
            collect.add(GFG.Geeks);
      
            // Displaying the collection
            System.out.println("The collection is: " + collect);
      
            EnumSet<GFG> e_set = EnumSet.copyOf(collect);
      
            // Displaying the final set
            System.out.println("The enum set is:" + e_set);
        }
    }

    
    

    Output:

    The collection is: [Welcome, World, Geeks]
    The enum set is:[Welcome, World, Geeks]
    
  2. The java.util.EnumSet.copyOf(EnumSet e_set) method in Java is used to copy all of the contents from an existing EnumSet i.e., e_set, to a new enum set.

    Syntax:

    New_Enum_Set = EnumSet.copyOf(EnumSet e_set)

    Parameters: The method accepts one parameter e_set of the object type of the enum and refers to the set whose values are to be copied into the New_Enum_Set.

    Return Values: The method does not return any values.

    Exceptions: The method throws NullPointerException when e_set is NULL.

    Below program illustrates the working of java.util.EnumSet.copyOf() method:




    // Java program to demonstrate copyOf() method
    import java.util.*;
      
    // Creating an enum of CARS type
    enum CARS {
        RANGE_ROVER,
        MUSTANG,
        CAMARO,
        AUDI,
        BMW
    }
    ;
      
    public class Enum_Set_Demo {
      
        public static void main(String[] args)
        {
      
            // Creating an empty EnumSet
            // Getting all elements from CARS
            EnumSet<CARS> e_set = EnumSet.allOf(CARS.class);        
      
            // Displaying the initial EnumSet
            System.out.println("Initial set is: " + e_set);
      
            // Copying the set
            EnumSet<CARS> new_set = EnumSet.copyOf(e_set);
      
            // Displaying the final set
            System.out.println("The new set is: " + new_set);
        }
    }

    
    

    Output:

    Initial set is: [RANGE_ROVER, MUSTANG, CAMARO, AUDI, BMW]
    The new set is: [RANGE_ROVER, MUSTANG, CAMARO, AUDI, BMW]
    


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