import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.regex.*;
import java.util.HashMap;
 
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
        String email = "riyajose@gmail.com your my rosymj@gmail.com";
        String regex="((?<!\\S)[^\\s@]{3}|(?!^)\\G)[^\\s@](?=[^@\\s]*@)";
        Pattern pattern = Pattern.compile(regex);
        String mask="$1*"; // String maskedEmail = email.replaceAll("\\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\\.[A-Z]{2,6}\\b", "xxxxxx");
        String email1 = pattern.matcher(email).replaceAll(mask);
        System.out.println("email : "+email);
        System.out.println("maskedEmail : "+email1);
	}
}

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