Hacker Rank Problem - Regex - Alien Username

Alien Username

The following is the solution to the Hacker Rank problem “Alien Username" using Java.  For other Hacker Rank problem solutions visit my Hacker Rank Solutions Page.

/**  * @author Arun.G  *  */ import java.io.*; import java.util.*; import java.text.*; import java.math.*; import java.util.regex.*; public class Solution {     public static void main(String[] args) {         /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */         Scanner sc = new Scanner(System.in);         int no = sc.nextInt();         while(no-->=0)         {             String word = sc.nextLine();             int count=0;             if(!word.equals(""))             {                 //for country                 String pattern ="^[._]{1}[0-9]{1,}[a-zA-Z]{0,}_{0,1}$";                 Pattern userNamePattern = Pattern.compile(pattern);                 Matcher m = userNamePattern.matcher(word);                 if(m.find())                 {                    System.out.println("VALID");                 }                 else                 {                     System.out.println("INVALID");                 }             }         }     } }