Thinking process

Two pointers, one starts from the beginning, one starts from the end, then moving to center

Don't need to worry about skip white spaces or any other special characters

public class Solution {
    public String reverseString(String s) {
        char[] chars = s.toCharArray();

        int left = 0;
        int right = chars.length - 1;

        while (left < right) {
            char tmp = chars[left];
            chars[left] = chars[right];
            chars[right] = tmp;
            left++;
            right--;
        }

        return new String(chars);   
    }
}