两句话中的不常见单词

import java.util.*;

class Solution884 {
    public static void main(String[] args) {
        new Solution884().uncommonFromSentences("apple apple", "banana");
    }

    public String[] uncommonFromSentences(String s1, String s2) {
        HashMap<String, Integer> m = new HashMap<String, Integer>();
        for (String s : s1.split(" ")) {
            m.put(s, m.getOrDefault(s, 0) + 1);
        }
        for (String s : s2.split(" ")) {
            m.put(s, m.getOrDefault(s, 0) + 1);
        }
        List<String> res = new ArrayList<>();
        for (Map.Entry<String, Integer> entry : m.entrySet()) {
            if (entry.getValue() == 1) {
                res.add(entry.getKey());
            }
        }
        System.out.println(res);
        return res.toArray(new String[0]);
    }
}