Reverse Words in a String II

Given an input string, reverse the string word by word. A word is defined as a sequence of non-space characters.
The input string does not contain leading or trailing spaces and the words are always separated by a single space.
For example,
Given s = "the sky is blue",
return "blue is sky the".
Could you do it in-place without allocating extra space?
Related problem: Rotate Array


public class Solution {
    public void reverseWords(char[] s) {
        reverse(s, 0, s.length - 1);
        int i = 0;
        while (i < s.length) {
            while (i < s.length && s[i] == ' ') i++;
            int begin = i;
            while (i < s.length && s[i] != ' ') i++;
            int end = i - 1;
            reverse(s, begin, end);
        }
    }
   
    private void reverse(char[] s, int start, int end) {
        while (start <= end) {
            char tmp = s[start];
            s[start] = s[end];
            s[end] = tmp;
            start++;
            end--;
        }
    }
}