151. Reverse Words in a String

Given an input string, reverse the string word by word.

For example,
Given s = "the sky is blue",
return "blue is sky the".

题目含义：翻转字符串中的单词的顺序，单词内容不变

    public String reverseWords(String s) {
        s = s.trim();
        String[]words = s.split("\s+");//正则表达式s表示匹配任何空白字符，+表示匹配一次或多次。
        if (words.length <2) return s;
        int low=0,high=words.length-1;
        while (low<high)
        {
            String temp = words[low];
            words[low] = words[high];
            words[high] = temp;
            low++;
            high--;
        }
        StringBuilder sb = new StringBuilder();
        for (String word:words)
        {
            sb.append(word).append(" ");
        }
        return sb.toString().trim();
    }
}