【剑指offer】翻转单词顺序列

【求助】
搞不懂样例为" "时我在牛客网上的结果是""，而在本地上测的结果是" "！！！

public class Solution {
    public static String ReverseSentence(String str) {

        if (str == null || str.length() <= 1) { // 处理" "的情况
            return str;
        }

        StringBuilder sb = new StringBuilder();
        String[] strs = str.split(" ");
        for (int i = strs.length - 1; i >= 0; i--) {
            sb.append(i == 0 ? strs[i] : strs[i] + " ");
        }
        return sb.toString();
    }
}