how to work with letters in java code example

Example 1: java manipulate alphabet list

String usernameInDatabase = "modernNerd";String passwordInDatabase = "mN123Java";String providedUsername = "modernnerd";String providedPassword = "mN123Java";if(providedUsername.equalsIgnoreCase(usernameInDatabase)){    //successful username comparison    //check the provided password    //this will fail    //if("mn123java".equals(passwordInDatabase)){}        //this will pass    if(providedPassword.equals(passwordInDatabase)){        System.out.println("Success! You are logged in.");    } else {        System.out.println("Wrong password. Try again.");    }} else {    //user provided wrong username    System.out.println("Wrong username. Try again.");}

Example 2: java manipulate alphabet list

String alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";int indexOfLetterD = alphabet.indexOf("D");//indexOfLetterD equals 3