class Solution {
public String reverseWords(String s) {
   
        String[] strings = s.trim().split(" ");
        StringBuilder sb=new StringBuilder();
 
        for(int i=strings.length-1;i>=0;i--){
            
            if (strings[i].equals("")) continue;
            if(i==0)  sb.append(strings[i]);
            else sb.append(strings[i]).append(" ");
      
        }
 return sb.toString();
}}

trim()去掉首尾空格
split()拼接