Uncommon Words from Two Sentences

给两个序列, 用空格隔开. 找两个序列中只出现一次的word. 先连起来, 然后再做.

class Solution {
    public String[] uncommonFromSentences(String A, String B) {
        Map<String, Integer> map = new HashMap<>();
        String C = A + " "+ B;
        List<String> list = new ArrayList<>();
        for (String w: C.split(" "))
            map.put(w, map.getOrDefault(w, 0) + 1);
         for (String s: C.split(" ")){
            if(map.get(s) == 1)
                list.add(s);
         }  
        String[] res = new String[list.size()];
        for(int i = 0 ; i < res.length; i++) {
            res[i] = list.get(i);
        }
        return res;
    }
}