186. Reverse Words in a String II

class Solution {
    public void reverseWords(char[] s) {
        reverse(s, 0, s.length - 1);

        int j = 0;
        while (j < s.length) {
            int i = j;
            while (j < s.length && s[j] != ' ') {
                j++;
            }

            reverse(s, i, j - 1);
            j++;
        }
    }

    private void reverse(char[] chars, int i, int j) {
        while (i < j) {
            swap(chars, i++, j--);
        }
    }

    private void swap(char[] chars, int i, int j) {
        char tmp = chars[i];
        chars[i] = chars[j];
        chars[j] = tmp;
    }
}

Reference