static public class Solution {

public String reverseWords(String s) {

if(s == null || s == "") return s;

return reverse(s.toCharArray()).reverse().toString();

}

public StringBuilder reverse(char[] chars){

StringBuilder sb = new StringBuilder();

int i = 0;

while (chars[i] == ' '){

i++;

}

for(; i < chars.length; i++){

if(chars[i] != ' '){

int temp = i;

while (temp < chars.length && chars[temp] != ' '){

temp ++;

}

for(int j = temp - 1; j >= i ; j-- ){

sb.append(chars[j]);

}

i = temp - 1;

}else{

sb.append(' ');

}

}

return sb;

}

}

public static void main(String[] args) {

System.out.println(new Solution().reverseWords(""));

}