How to make uppercase with charAt() method in Java?

I am trying to make a program where a input an email from the user. I have to create a username from the email by deleting the part that comes after ‘@’ and I will display that username to the user. I will ignore the numbers and after a '.' and I will uppercase the next char.

Example :

email = “something.someone.98@gmail.com” ; username = “SomethingSomeone”

email = “something.someone@icloud.com”; username = “SomethingSomeone”

package core_java.JavaExercise.Two;

import java.util.Scanner;

import static java.lang.System.in;
import static java.lang.System.out;

public class Java_String_Exercise_03 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(in);

        out.print("Enter your email address: ");
        String email = sc.next();

        String userName = "";

        for (int i = 1 ; i < email.length() ; i++) {
            Boolean digitCheck = Character.isDigit(email.charAt(i));
            if(digitCheck) {
                userName += "";
            } else if (email.charAt(i) == '@') {
                break;
            } else if (email.charAt(i) == '.') {
                if (Character.isDigit(email.charAt(i+1))) {
                    userName += "";
                } else {
                    userName += "" + String.valueOf(email.charAt(++i)).toUpperCase();
                }
            } else {
                userName += email.charAt(i);
            }
        }
        out.printf("Your username is %s.", userName);
    }
}

I have solved the problem however is there any efficient way of doing this code?

The following condition means that the last value isn't the value you loop for, that isn't a reason to stop looking for you value. As it isn't the first, and not the last, your stop, but haven't search in the middle

else if (arr[arr.length - 1] != target) {
    out.printf("Your target = %d has not been found.", target);
    break;
}

You need to have search through the whole array before being able to say "not found"

boolean found = false;
for (int i = 0; i < arr.length; i++) {
    if (arr[i] == target) {
        out.printf("Target = %d has found at the index of %d\n", target, i);
        found = true;
        break;
    }
}

if (!found) {
    out.printf("Your target = %d has not been found.\n", target);
}