翻转单词顺序

输入一个英文句子，翻转句子中单词的顺序，但单词内字符的顺序不变，为简单起见，标点符号和普通字母一样处理

示例
输入：I am a student.
输出：student. a am I

思路：按照空格分割字符串，交换字符串

public class ReverseWordsInSentence {

    private String reverse(String str) {
        String[] strs = str.split(" ");
        int start = 0;
        int end = strs.length - 1;
        while (start < end) {
            String t = strs[start];
            strs[start] = strs[end];
            strs[end] = t;
            start++;
            end--;
        }

        StringBuffer sb = new StringBuffer();
        for (String s : strs) {
            sb.append(s).append(" ");
        }
        return sb.toString().trim();
    }
}