reverse individual words

// Online Java Compiler
// Use this editor to write, compile and run your Java code online
import java.util.*;
class Main {
    public static void main(String[] args) {
       String s="hello    world hi";
       
       String[] str=s.split("\s+");
       ArrayList<String> ar=new ArrayList<>();
       for(String x:str){
               StringBuilder sb=new StringBuilder(x);
         
           ar.add(sb.reverse().toString());
       }
       StringBuilder sb=new StringBuilder();
       int j=0;
       int k=0;
       boolean iswhite=false;
      for(int i=0;i<s.length();i++){
           if(Character.isLetter(s.charAt(i))){
               if(iswhite)
                j++;
               sb.append(ar.get(j).charAt(k));
               k++;
               iswhite=false;
               
               
           }else{
               sb.append(" ");
               iswhite=true;
               k=0;
           }
      }
       System.out.println(sb.toString());
    }
    // public static string reverse(String res){
    //     StringBuilder sb=new StringBuilder(res);
    //     return sb.revrese().toString();
    // }
}