EnumSet.copyOf(EnumSet) in Java

EnumSet.copyOf(EnumSet): This method is available in java.util.EnumSet class of Java.

Syntax:

<K> EnumSet<K> java.util.EnumSet.copyOf(EnumSet<K> s)

This method takes one argument. This method creates an enum set with the same element type as the specified enumset, initially containing the same elements

Parameters: One parameter is required for this method.

s: the enum set from which to initialize this enum set.

Returns: A copy of the specified enum set.

Throws:

NullPointerException - if s is null

Approach 1: When no exception

Java

import java.util.EnumSet;

public class EnumSetcopyOf2 {
    public enum Colour {
        RED, GREEN, YELLOW, ORANGE
    };

    public static void main(String[] args) {

        EnumSet<Colour> enumSet = EnumSet.allOf(Colour.class);

        System.out.println(EnumSet.copyOf(enumSet));

    }
}

Output:

[RED, GREEN, YELLOW, ORANGE]

Approach 2: NullPointerException 

Java

import java.util.EnumSet;

public class EnumSetcopyOf2 {
    public enum Colour {
        RED, GREEN, YELLOW, ORANGE
    };

    public static void main(String[] args) {

        System.out.println(EnumSet.copyOf(null));

    }
}

Output:

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.util.EnumSet.clone()" because "s" is null
	at java.base/java.util.EnumSet.copyOf(EnumSet.java:153)