151. 翻转字符串里的单词

class Solution {
    public String reverseWords(String s) {
       String trim = s.trim();
        int left = trim.length() - 1;
        int right = trim.length() - 1;
        StringBuilder sb = new StringBuilder();
        while (left >= 0) {
            while (left >= 0 && trim.charAt(left) != ' ') {
                left--;
            }
            String substring = trim.substring(left + 1, right + 1) + " ";
            sb.append(substring);
            while (left >= 0 && trim.charAt(left) == ' ') {
                left--;
            }
            right = left;
        }
        return sb.toString().trim();
    }
}