[LeetCode]Reverse Words in a String

题目：给定一个字符串数组，翻转数组中的单词，样例：the sky is blue  输出  blue is sky the

算法：字符串处理，要注意一些细节： 

1. 字符串为空 

2. 字符串由空白组成

3. 字符串前度和后度空白

4. 字符串之间充满了空白

public class Solution {    public String reverseWords(String s) {        if (null == s) {        // case when s is null        return null;        }                int length = s.length();        ArrayList<String> words = new ArrayList<String>();        for (int i=0; i<length; ) {        String word = new String();        while (i<length && (' '==s.charAt(i) || '\t'==s.charAt(i))) {        ++i;        }        while (i<length && ' '!=s.charAt(i) && '\t'!=s.charAt(i)) {        word += s.charAt(i++);        }        if (word.length() >= 1) {        words.add(word);        }        }        if (words.isEmpty()) {        return "";        } else {        String reverse = new String();        boolean isFirstWord = true;        int nWords = words.size();        for (int j=nWords-1; j>=0; --j) {        if (isFirstWord) {        reverse += words.get(j);        isFirstWord = false;        } else {        reverse += (" " + words.get(j));        }        }        return reverse;        }    }}