Reversing a domain name string in Java Given a dot separated domain name, reverse the domain elements.


Example:

codereview.stackexchange.com -&gt; com.stackexchange.codereview
google.com -&gt; com.google


I just wanted some suggestions to improve my code. Or if you can suggest a better way, please do so.

package practice;

import java.util.Scanner;
import java.util.StringTokenizer;


public class ReverseDomainName
{
    public static void main(String args[])
    {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter the domain name to be reversed");
        String domain = sc.nextLine();
        sc.close();
        ReverseDomainName obj = new ReverseDomainName();
        String reversedDomainName = obj.reverseDomainNameString(domain);
        System.out.println("The reversed Domain Name = "+reversedDomainName);
    }

    public String reverseDomainNameString(String s)
    {
        String reverse1 = "",word ="" ;
        int i;

        StringTokenizer st = new StringTokenizer(s,"."); 
        int len = st.countTokens();

        /*
         * The check is performed so that instead of com.stackexchange.codereview.
         * we can get the proper com.stackexhange.codereview  so no
         * extra dot
         */

        word  = st.nextToken();
        reverse1 = word+reverse1;


        for(i=1;i&lt;len;i++)
        {
            word = st.nextToken();
            reverse1 = word +"."+reverse1;

        }

        return reverse1;
    }

}
StringTokenizer is an OK solution, but I think that String.split() would lead to a less verbose solution.

Here is a Java 8 solution that uses split():

public static String reverseDomainNameString(String s) {
    List&lt;String&gt; components = Arrays.asList(s.split("\\."));
    Collections.reverse(components);
    return String.join(".", components.toArray(new String[0]));
}


Without Java 8's String.join(), though, the solution would be more tedious.  Note that it might be a good idea to ensure that the string is non-empty, otherwise components[0] (or st.nextToken() in your original solution) would crash.

public static String reverse(String s) {
    if (s == null || s.isEmpty()) return s;
    String[] components = s.split("\\.");
    StringBuilder result = new StringBuilder(s.length());
    for (int i = components.length - 1; i &gt; 0; i--) {
        result.append(components[i]).append(".");
    }
    return result.append(components[0]).toString();
}