Partition into Even and Odd

/*
 * Problem : Split numbers.
 * Input   : n, then n integers.
 * Output  : Two lines.
 * Approach: Partition.
 * Time    : O(n)
 * Space   : O(n)
 * Java    : 8 or newer.
 */
import java.util.Scanner;

public class Main {
    // This method solves the task. It receives the input and returns the answer.
    static String[] solve(int[] a) {
        // Step 1: partitioningBy splits a stream into two lists: the values with a true test and the values with a false test.
        java.util.Map<Boolean, java.util.List<Integer>> parts = java.util.Arrays.stream(a).boxed()
                .collect(java.util.stream.Collectors.partitioningBy(value -> value % 2 == 0));

        // Step 2: Join each list into text. Java % keeps the sign, so -3 % 2 is -1 (not 0), and -3 is correctly odd.
        String evens = parts.get(true).stream().map(String::valueOf).collect(java.util.stream.Collectors.joining(" "));
        String odds = parts.get(false).stream().map(String::valueOf).collect(java.util.stream.Collectors.joining(" "));
        return new String[] {"evens: " + evens, "odds: " + odds};
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int size = scanner.nextInt();
        int[] a = new int[size];
        for (int i = 0; i < size; i++) {
            a[i] = scanner.nextInt();
        }
        System.out.println(String.join("\n", solve(a)));
    }
}