In Java 8, we can use .toArray() to convert a Stream into an Array.

1. Stream -> String[]

package com.mkyong;
import java.util.Arrays;
public class StreamString {
    public static void main(String[] args) {
        String lines = "I Love Java 8 Stream!";
        // split by space, uppercase, and convert to Array
        String[] result = Arrays.stream(lines.split("\\s+"))
			.map(String::toUpperCase)
			.toArray(String[]::new);
        for (String s : result) {
            System.out.println(s);

Output

LOVE
JAVA
STREAM!

2. IntStream -> Integer[] or int[]

2.1 Stream to Integer[]

package com.mkyong;
import java.util.Arrays;
public class StreamInt1 {
    public static void main(String[] args) {
        int[] num = {1, 2, 3, 4, 5};
        Integer[] result = Arrays.stream(num)
			.map(x -> x * 2)
			.boxed()
			.toArray(Integer[]::new);
        System.out.println(Arrays.asList(result));

Output

[2, 4, 6, 8, 10]

2.2 Stream to int[]

package com.mkyong;
import java.util.Arrays;
import java.util.stream.IntStream;
import java.util.stream.Stream;
public class StreamInt2 {
    public static void main(String[] args) {
        // IntStream -> int[]
        int[] stream1 = IntStream.rangeClosed(1, 5).toArray();
        System.out.println(Arrays.toString(stream1));
        // Stream<Integer> -> int[]
        Stream<Integer> stream2 = Stream.of(1, 2, 3, 4, 5);
        int[] result = stream2.mapToInt(x -> x).toArray();
        System.out.println(Arrays.toString(result));

Output

[1, 2, 3, 4, 5]
[1, 2, 3, 4, 5]