/*
Date 			: 		11 October 2013
Author			:		Shivam Tiwari [shivamtiwari1011@gmail.com]
Organization		:		http://mycodedock.blogspot.in/
Description		:		http://mycodedock.blogspot.in/2013/10/validate-username-string-java.html
*/
 
import java.util.Scanner;
import java.util.regex.Pattern;
import java.util.regex.Matcher;
 
public class Main{
	public static void main(String[] args){
 
		//declaring required variables
		String inputString, findPattern;
 
		//creating a new Scanner object
		Scanner scannerObj = new Scanner(System.in);
 
		//username can have a-z ans 0-9 and _ and -
		//username must be 6 - 12 characters long
		findPattern = "^[a-z0-9_-]{6,12}$";
 
		System.out.println("Enter your chosen username : ");
 
		//get inputString
		inputString = scannerObj.nextLine();
 
		//create a pattern object
		Pattern patternObj = Pattern.compile(findPattern);
 
		//create a matcher object
		Matcher matcherObj = patternObj.matcher(inputString);
 
		if(matcherObj.find()){
			System.out.println("This is a valid usernamr : " + inputString);
		}
		else{
			System.out.println("This is NOT a valid username : " + inputString);
		}
	}
}