/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.Collections;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		String email = "dineshkani.n@gmail.com";
		String regex = "(^.{1})|((.{1})(@.*))";
		String replace = email.replaceAll(regex, "");
		String result = email.replace(
				replace, 
				String.join("", Collections.nCopies(replace.length(), "*"))
		);
		System.out.println(result);
	}
}

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