Java Stream toArray()

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In this guide, you will learn about the Stream toArray() method in Java programming and how to use it with an example.

1. Stream toArray() Method Overview

Definition:

The Stream.toArray() method is a terminal operation used to obtain an array containing the elements of the stream.

Syntax:

Object[] toArray()

<A> A[] toArray(IntFunction<A[]> generator)

Parameters:

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

Key Points:

- It is a terminal operation, which means it ends the stream pipeline.

- The toArray() method comes in two variants:

1. One that produces an Object[].

2. Another that produces an array of a type determined by the provided generator function.

- If the stream is infinite, a java.lang.OutOfMemoryError may be thrown when trying to allocate an array of infinite length.

- The generator function gives more control over the runtime type of the output array.

2. Stream toArray() Method Example

import java.util.stream.Stream;

public class StreamToArrayExample {
    public static void main(String[] args) {
        Stream<String> fruitStream = Stream.of("Apple", "Banana", "Cherry", "Date", "Elderberry");

        // Convert the stream into an array of strings
        String[] fruitArray = fruitStream.toArray(String[]::new);

        // Print the array
        for (String fruit : fruitArray) {
            System.out.println(fruit);
        }
    }
}

Output:

Apple
Banana
Cherry
Date
Elderberry

Explanation:

In the provided example: We have a stream of fruit names. Using toArray(), we convert this stream into an array of strings. The String[]::new is a constructor reference used as the generator function to produce the output array of the desired type. We then iterate through the array and print each fruit.

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