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How to verify OTP in Java using simple loop?

I'm a Java beginner and my project consists of creating a simple program to register users for an alumni center. The process creates an ID and then provides the new user with an OTP. Next is the login (Enter ID:, Enter OTP: ).
My OTP verification method is not working. It seems to be a problem with the IF.equals declaration, the process jumps straight to the ELSE condition.
Any suggestions why?
Here is my code:
class Main {
static NewRegandLogin newRegAndLogin = new NewRegandLogin(null, null, null, null, null, null);
static ArrayList<NewRegandLogin> loginInformation = new ArrayList<>();
public static void main(String[] args) {
System.out.println(" WELCOME TO THE ALUMNI SHE-CODES SYSTEM ");
System.out.println("_________________________________\n - New Alumni registration - \n");
System.out.println("");
newRegAndLogin.registerNewGrad();
System.out.println();
System.out.println("_________________________________");
System.out.println();
System.out.println("Your new Alumni ID is: " + newRegAndLogin.getAlumniId());
System.out.println();
System.out.println("Your temporary password is:");
System.out.println(newRegAndLogin.oTp(8));
loginInformation.add(newRegAndLogin);
System.out.println("_________________________________");
System.out.println("_________________________________\n - Alumni Login - \n");
System.out.println("");
newRegAndLogin.login();
System.out.println("");
System.out.println("Please make a list of completed Courses: -->Enter 'S' to stop adding courses<--");
newRegAndLogin.setAlumniCourses();
System.out.println("_________________________________");
newRegAndLogin.setLinkedInPage();
loginInformation.add(newRegAndLogin);
//printAlumniProfile();
System.out.println("_________________________________");
newRegAndLogin.jobOffer();
}
void login() {
System.out.print("ID: ");
alumniIdImput = scanner.nextLine();
idVerification();
do {
System.out.println("Password (OTP if logging in for the first time): ");
passwordImput = scanner.nextLine();
oTpFromImput = passwordImput.toCharArray();
oTpVerification();
} while (isPasswordCorrect=false);
void oTpVerification() {
isPasswordCorrect = false;
if (oTpFromImput.equals(oTp(8))) {
isPasswordCorrect = true;
System.out.println("Logging In.....");
}else {
isPasswordCorrect = false;
System.out.println("Incorrect password.\nPlease enter valid password: 8 alpha numeric
characters(Aa,123,#,#,$,%)");
}
}
This is the oTp method
char[] oTp (int length) {
String capitalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
String smallChars = "abcdefghijklmnopqrstuvwxyz";
String numbers = "0123456789";
String symbols = "!##$%^&*_-=+/.?<>";
String values = capitalChars + smallChars + numbers + symbols;
Random oneTimePassword = new Random();
char[] password = new char[length];
for(int i = 0; i<length;i++) {
password[i] = values.charAt(oneTimePassword.nextInt(values.length()));
}
return password;
}

It seems you built a guessing game, not an OTP verification code.
You first read the OTP from user, and only then randomly generate one to copare to it.
Basically, you code expects the user to guess a random 8 character password that has not been created you, which is basically impossible...
You need to generate to OTP first, show it to the user, then ask them to input it.

I see your logic code is generate OTP code after User input. It seem so wierd bro.
Whenever you call oTp(8) function will generate new OTP.
Use should generate OTP first then store somewhere, then User input and compare it.

You need to store the generated otp somewhere. Then compare it with the input otp. Right now you are comparing it with the otp(8). And otp(8) always returns a new otp.

Why will my continue statement not restart my while loop?

I am trying to complete an authentication program for my final project. I am checking for user authentication, if the user info doesn't match the credentials file, the output tells them this and then prompts for username and password while increment an attemptCounter. The only portion I am experiencing an issue with is when I test and incorrect attempt followed by a correct attempt, the while loop will not restart my authentication procedure, instead it simple says incorrect login again. Why isn't my continue statement restarting my while loop iteration?
I tired looking around for this answer on the forum and food nothing specific to my issue. I tried moving my conditional statement as well to see if it was in the wrong spot for my continue to work but it fixed nothing. Compiler says both of my continue statements are unnecessary.
//prompting user for username
System.out.println("Please enter your username (\"L\" to logout \"Q\" to quit): ");
username = scnr.nextLine();
//evaluating if user wants to quit immediately
if(username.equals("Q")) {
System.exit(0);
}
//prompting user for password and storing to password field
System.out.println("Please enter your password: ");
password = scnr.nextLine();
System.out.print("\n");
//while loop that contains the authentication and authorization logic
while (!username.equals("Q") && attemptCounter < 2){
//calling of hashInput method of MD5Hash class to return the hashed user password
userHashedPassword = userHash.hashInput(password);
//while loop to open the credentials for authentication comparison
while (cfScnr.hasNextLine()) {
//assigning the files scanned next line to a field for comparison
line = cfScnr.nextLine();
//conditional statement to determine if username and password are contained on the line
//will break file loop as soon as line contains the user's username and password
//statement logic used to return the role string and remove extra characters and white space
if (line.contains(username) && line.contains(userHashedPassword)) {
dqLocation = line.lastIndexOf('"');
role = line.substring(dqLocation);
role = role.replaceAll("\\s+", "");
role = role.replace("\"", "");
break;
}
}
//conditional statement used to determine if previous loops condtional statement was meant
//if it wasn't this condition will inform the user of incorrect username and/or password
//inform them of attempts remaining and prompt them for a new username and password while
//tracking the attempts and it they want to quit. If Q isn't entered main while loop will restart authentication
if (role == null){
attemptCounter++;
System.out.println("Username or password incorrect. " + (3 - attemptCounter) + " attempts remaining.");
System.out.println("Please enter your username (\"L\" to logout \"Q\" to quit): ");
username = scnr.nextLine();
if(username.equals("Q")) {
System.exit(0);
}
System.out.println("Please enter your password: ");
password = scnr.nextLine();
continue;
}
//this conditional statement runs only when the user is authenticated
else {
//creating new file object and scanner object to scan the role file
File rFile = new File("src\\zooauthenticationsystem\\" + role + ".txt");
Scanner rfScnr = new Scanner(rFile);
//while loop to parse through the role file and output the lines of the file to the console
while (rfScnr.hasNextLine()){
rolePrint = rfScnr.nextLine();
System.out.println(rolePrint);
}
//prompting user if they would like to logout or simply quit the program
System.out.println("\nPress \"L\" to logout and \"Q\" to quit.");
userDecision = scnr.nextLine();
//conditional statement to determine their input, and resetting role to null to reset authentication loop conditional statements, restarts main while loop
if (userDecision.equals("L")){
System.out.println("Please enter your username: ");
username = scnr.nextLine();
if(username.equals("Q")) {
System.exit(0);
}
System.out.println("Please enter your password: ");
password = scnr.nextLine();
System.out.print("\n");
role = null;
continue;
}

Let's get rid of most of your code, let's format the code better, and let's leave only the control structures to see what the continue statements are doing:
while (!username.equals("Q") && attemptCounter < 2) {
userHashedPassword = userHash.hashInput(password);
while (cfScnr.hasNextLine()) {
line = cfScnr.nextLine();
if (line.contains(username) && line.contains(userHashedPassword)) {
// ... do some stuff
break;
}
}
if (role == null) {
// ... do some stuff
continue; // **** (A) ****
} else {
// ... do some stuff
if (userDecision.equals("L")){
// ... do some stuff
continue; // **** (B) ****
}
}
}
If line (A) is reached, you're in the if (roll == null) block, the else will never be entered, and the while loop will repeat regardless of the continue statement making continue unnecessary and distracting.
Likewise if line (B) is reached, you're in the last control block of the while loop, and so the loop will continue regardless of the continue statement making continue unnecessary and distracting.

How to check the user input is an integer or not with Scanner?

I want the country codes are integer that input by the user. I want an error message to be show when user inputs a code which is not an integer. How can I do this? The program is to ask user to enter country name and country code. In which user will input the country code. But if user inputs a character I want a message to be shown saying Invalid Input.
System.out.println("Enter country name:");
countryName = in.nextLine();
System.out.println("Enter country code:");
int codeNumber = in.nextInt();
in.nextLine();

If the input is not an int value, then Scanner's nextInt() (look here for API) method throws InputMismatchException, which you can catch and then ask the user to re-enter the 'country code' again as shown below:
Scanner in = new Scanner(System.in);
boolean isNumeric = false;//This will be set to true when numeric val entered
while(!isNumeric)
try {
System.out.println("Enter country code:");
int codeNumber = in.nextInt();
in.nextLine();
isNumeric = true;//numeric value entered, so break the while loop
System.out.println("codeNumber ::"+codeNumber);
} catch(InputMismatchException ime) {
//Display Error message
System.out.println("Invalid character found,
Please enter numeric values only !!");
in.nextLine();//Advance the scanner
}

One simple way of doing it, is reading a line for the numbers as you did with the name, and then checking witha Regex (Regular Expression) to see if contains only numbers, with the matches method of string, codeNumber.matches("\\d+"), it returns a boolean if is false, then it's not a number and you can print your error message.
System.out.println("Enter country name:");
countryName = in.nextLine();
System.out.println("Enter country code:");
String codeNumber = in.nextLine();
if (codeNumber.matches("\\d+")){
// is a number
} else {
System.out.println("Please, inform only numbers");
}

You can do something like this, by first getting the input as a string, then try to convert the string to an integer, then outputs an error message if it can't:
String code= in.nextLine();
try
{
// the String to int conversion happens here
int codeNumber = Integer.parseInt(code);
}
catch (NumberFormatException nfe)
{
System.out.println("Invalid Input. NumberFormatException: " + nfe.getMessage());
}

You could instead check hasNextInt then call nextInt
int codeNumber;
System.out.println("Enter country code:");
if(in.hasNextInt())
{
codeNumber = in.nextInt();
}
else
{
System.out.println("Invalid Code !!");
}

If you are creating your own custom exception class, then use regex to check if the input string is an integer or not.
private final String regex = "[0-9]";
Then, check if the input follows the regex pattern.
if (codeNumber.matches(regex)) {
// do stuff.
} else {
throw new InputMismatchException(codeNumber);
}
You can use build in InputMismatchException if you are not creating your custom exception handler.

I need help on the Java Scanner Code

So I need help on this code. This code is all in one so ignore the spaces but I need to write another scanner in the way bottom of the code and if I do add
String feeling = in.nextLine(); at the very end it does not work. I need a it so that I can write my feelings so that I can make jarvis answer but the string does not work and java ignores the string and goes right on to the next part. It starts from the middle.
Scanner in = new Scanner(System.in);
System.out.println("Type User Name:");
String userName = in.nextLine();
System.out.println("PASSWORD:");
int passcodeFromUser=in.nextInt();
int passcode = 2015;
if (passcodeFromUser == passcode) {
System.out.println("Welcome Mr." + userName + "!");
Random random = new Random(userName.hashCode());
System.out.println("Mr." + userName + ", You are now recognized and you are now able to command me.");
System.out.println("I was created by John Choi");
System.out.println("JARVIS stands for Just A Rather Very Intelligent System");
System.out.println("How are you today Mr." + userName + "?");
}
So if I add this code at the back it does not work. It ignores and says Oh. Mr is feeling.
String feeling = in.nextLine();
System.out.println("Oh. Mr." + userName + "is feeling" + feeling + ".")

That is because your nextInt invocation does not actually parse a line feed.
Quoting the API, Scanner#nextInt:
Scans the next token of the input as an int.
(focus on the token part here)
Here's one (but not the only) way to fix it:
Integer passcodeFromUser = null;
try {
passcodeFromUser= Integer.parseInt(in.nextLine());
}
catch (NumberFormatException nfe) {
// TODO handle non-numeric password
}
... instead of int passcodeFromUser=in.nextInt();.
You can also loop the parsing of the Integer so that you print an error message when catching the NumberFormatException and don't break the loop until you have a valid numeric passcode.

You can consume the \n character:
in.nextLine();
String feeling = in.nextLine();
So just putting in.nextLine() before the code you were going to add will easily fix your problem.

Make an email list, by entering only recipient names

I want to make a simple code, that prompts you to enter names, separated by comma or just a space, and when you click enter, to take every one word you entered, and put a #gmail.com at the end of it, how can I do it?
That's what I have for now
Scanner input = new Scanner(System.in);
String mail = "#gmail.com";
String names;
System.out.println("Enter names: ");
names = input.next();
System.out.println(names + mail);

This should be everything you asked for, if you put a list of names separated by commas it will loop through them, otherwise it will just print a single name.
Scanner input = new Scanner(System.in);
String mail = "#gmail.com";
System.out.println("Enter names: ");
String names = input.next();
if(names.contains(",")) {
for(String name : names.split(",")) {
System.out.println(name + mail);
}
} else {
System.out.println(names + mail);
}
Hope that helps.

Not knowing what language this is, here's the pseudo-code:
names = input.next();
namesArray = names.split(" ") -- replace with your preferred delimiter
foreach name in namesArray
print name + mail