Character Frequency Counter with a HashMap

import java.util.*;

public class CharacterFrequency {
    public static void main(String[] args) {
        Map<Character, Integer> counts = countCharacters("hello world");

        List<Map.Entry<Character, Integer>> entries = new ArrayList<>(counts.entrySet());
        entries.sort(Map.Entry.<Character, Integer>comparingByValue().reversed()
                              .thenComparing(Map.Entry.comparingByKey()));

        for (Map.Entry<Character, Integer> entry : entries) {
            System.out.println("'" + entry.getKey() + "': " + entry.getValue());
        }
    }

    // O(n) time. merge() inserts 1 for a new character, or adds 1 to the existing count.
    static Map<Character, Integer> countCharacters(String text) {
        Map<Character, Integer> counts = new HashMap<>();
        for (char c : text.toCharArray()) {
            if (c == ' ') continue;
            counts.merge(c, 1, Integer::sum);
        }
        return counts;
    }
}