dns - Tracing a bug in a "reverse domain" program in Java -

my code supposed reverse domain. example, if input www.google.com.uk, should print uk.com.google.www

my problem code prints uk.com..google.www

i can't figure . comes or how remove it. did tracing , found www.stack.com.edu.uk return uk.edu..com..stack.www

import java.util.*;  public class domainreverse {        public static void main(string[] args) {         scanner sc = new scanner(system.in);         string domain = sc.nextline();         int x;         int start = 0;         string reversed_domain = "";         boolean flag = false;           do{              x = domain.indexof(".",start+1);             if(x==-1){                 flag = true;                 break;             }             reversed_domain = domain.substring(start,x+1) +reversed_domain;              start = x;           } while(flag==false);         int length = domain.length();         int z = domain.lastindexof(".");         string enddomain = domain.substring(z+1,length);         reversed_domain = enddomain+reversed_domain;         int p = reversed_domain.lastindexof(".");         reversed_domain = reversed_domain.substring(0,p);            system.out.print(reversed_domain);        }  }