EnumSet toArray(IntFunction) in Java

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

Syntax:

<K> K[] java.util.Collection.toArray(IntFunction<K[]> generator)

This method takes one argument. This method returns an array containing all of the elements in this collection, using the provided generator function to allocate the returned array.

Parameters: One parameter is required for this method.

generator: a function that produces a new array of the desired type and the provided length.

Returns: an array containing all of the elements in this collection.

Throws:

1. ArrayStoreException - if the runtime type of any element in this collection is not assignable to the runtime component type of the generated array.

2. NullPointerException - if the generator function is null.

Approach 1: When no exception

Java

import java.util.Arrays;
import java.util.EnumSet;
import java.util.function.IntFunction;

public class EnumSettoArray2 {
    public enum Colour {
        RED, GREEN, YELLOW, ORANGE
    };

    public static void main(String[] args) {

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

        IntFunction<Colour[]> intFunction = 
              new IntFunction<EnumSettoArray2.Colour[]>() {

            @Override
            public Colour[] apply(int value) {
                Colour[] colours = { Colour.RED, Colour.GREEN };
                return colours;

            }
        };

        System.out.println(Arrays.toString(enumSet.toArray(
                                                intFunction)));

    }
}

Output:

[RED, GREEN, YELLOW, ORANGE]

Approach 2: NullPointerException 

Java

import java.util.Arrays;
import java.util.EnumSet;
import java.util.function.IntFunction;

public class EnumSettoArray2 {
    public enum Colour {
        RED, GREEN, YELLOW, ORANGE
    };

    public static void main(String[] args) {

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

        IntFunction<Colour[]> intFunction = null;

        System.out.println(Arrays.toString(enumSet.toArray(
                                               intFunction)));

    }
}

Output:

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.util.function.IntFunction.apply(int)" because "generator" is null
	at java.base/java.util.Collection.toArray(Collection.java:413)