Find All Anagrams in a Text

/*
 * Problem : Process two words.
 * Input   : Two words separated by a space.
 * Output  : Start indexes or none.
 * Approach: A text and a pattern.
 * Time    : O(n)
 * Space   : O(1)
 * 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(String a, String b) {
        // Step 1: If the pattern is longer than the text, no part can match.
        if (b.length() > a.length()) {
            return "none";
        }
        // Step 2: "need" counts the letters of the pattern. "window" counts the letters in the current part of the text.
        int[] need = new int[26];
        int[] window = new int[26];
        for (int i = 0; i < b.length(); i++) {
            need[b.charAt(i) - 'a']++;
            window[a.charAt(i) - 'a']++;
        }
        StringBuilder result = new StringBuilder();
        for (int start = 0; ; start++) {
            // Step 3: The part is an anagram when both counts are equal.
            if (java.util.Arrays.equals(need, window)) {
                result.append(result.length() == 0 ? "" : " ").append(start);
            }
            // Step 4: Slide by one: add the next letter on the right and remove the first letter on the left.
            int next = start + b.length();
            if (next >= a.length()) {
                break;
            }
            window[a.charAt(next) - 'a']++;
            window[a.charAt(start) - 'a']--;
        }
        return result.length() == 0 ? "none" : result.toString();
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String a = scanner.next();
        String b = scanner.next();
        System.out.println(solve(a, b));
    }
}