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".

先要去除首尾两端的空格。 中间可能有多个连续空格， 所以split的时候要用regex。 eg： "    a     b     "

public class Solution {
    public String reverseWords(String s) {
        String t = s.trim();
        String[] pieces = t.split("[ ]+");
        int size = pieces.length;
        if(size == 0) return t;
        StringBuilder sb = new StringBuilder();
        for(int i = 0; i < size - 1; i ++){
            sb.append(pieces[size - 1 - i]);
            sb.append(" ");
        }
        sb.append(pieces[0]);
        return sb.toString();
    }
}