Question

I made an ATM program. I have a try catch that will ask for the user to type in their pin number. The pin number must be 5 digits. So the exception will check if it is 5 digits or not but the exception handling is not working. No matter what number I type in, it always says invalid number.

Here is my code the try catch is at the top of the program and the exception handling checkNumber is at the bottom of the program..

import java.util.ArrayList;
import java.util.Scanner;

public class BankMain
{
    private double availableBal = 80;
    private double totalBal = 100;
    private double availableBal2 = 480;
    private double totalBal2 = 500;
    private double availableBal3 = 80;
    private double totalBal3 = 100;
    ArrayList<Integer> cardNum = new ArrayList<Integer>();
    static Scanner input = new Scanner(System.in);

    private String error; // String the error from the exception
    {
        error = "error";
    }

    public void cardNumbers()
    {

        Scanner cards = new Scanner(System.in);
        Scanner input = new Scanner(System.in);
        Scanner keyboard = new Scanner(System.in);

        try
        {

            System.out.println("Please select a 5 digit card number");

            cardNum.add(input.nextInt());
            checkNumber();

        }

        catch (invalidNumber err)
        {

            System.out.println("Caught Error: " + err.getError());
        }

        System.out.println("Thank you! You're card number is " + cardNum);

        System.out.println("Type 'c' to go back to main menu.");
        String value = keyboard.next();

        if (value.equalsIgnoreCase("c"))
        {
            menu();

        }

        else if (!keyboard.equals('c'))
        {

            System.out.println("Invalid Entry!");

        }

    }

    public void menu()
    {

        System.out.println("ATM Menu:");
        System.out.println();
        System.out.println("1 = Create Account");
        System.out.println("2 = Account Login");
        System.out.println("3 = Exit ATM");
        query();
    }

    public void startAtm()
    {
        menu();

    }

    public void drawMainMenu()
    {

        AccountMain main3 = new AccountMain();
        int selection;

        System.out.println("\nATM main menu:");
        System.out.println("1 - View account balance");
        System.out.println("2 - Withdraw funds");
        System.out.println("3 - Add funds");
        System.out.println("4 - Back to Account Menu");
        System.out.println("5 - Terminate transaction");
        System.out.print("Choice: ");
        selection = input.nextInt();

        switch (selection)
        {
        case 1:
            viewAccountInfo();
            break;
        case 2:
            withdraw();
            break;
        case 3:
            addFunds();
            break;
        case 4:
            AccountMain.selectAccount();
            break;
        case 5:
            System.out.println("Thank you for using this ATM!!! goodbye");
        }
    }

    public void viewAccountInfo()
    {
        System.out.println("Account Information:");
        System.out.println("\t--Total balance: $" + totalBal);
        System.out.println("\t--Available balance: $" + availableBal);
        drawMainMenu();
    }

    public void viewAccountInfo2()
    {
        System.out.println("Account Information:");
        System.out.println("\t--Total balance: $" + totalBal2);
        System.out.println("\t--Available balance: $" + availableBal2);
        drawMainMenu();
    }

    public void deposit(int depAmount)
    {
        System.out.println("\n***Please insert your money now...***");
        totalBal = totalBal + depAmount;
        availableBal = availableBal + depAmount;
    }

    public void checkNsf(int withdrawAmount)
    {
        if (totalBal - withdrawAmount < 0)
            System.out.println("\n***ERROR!!! Insufficient funds in you accout***");
        else
        {
            totalBal = totalBal - withdrawAmount;
            availableBal = availableBal - withdrawAmount;
            System.out.println("\n***Please take your money now...***");
        }
    }

    public void addFunds()
    {
        int addSelection;

        System.out.println("Deposit funds:");
        System.out.println("1 - $20");
        System.out.println("2 - $40");
        System.out.println("3 - $60");
        System.out.println("4 - $100");
        System.out.println("5 - Back to main menu");
        System.out.print("Choice: ");
        addSelection = input.nextInt();

        switch (addSelection)
        {
        case 1:
            deposit(20);
            drawMainMenu();
            break;
        case 2:
            deposit(40);
            drawMainMenu();
            break;
        case 3:
            deposit(60);
            drawMainMenu();
            break;
        case 4:
            deposit(100);
            drawMainMenu();
            break;
        case 5:
            drawMainMenu();
            break;
        }
    }

    public void withdraw()
    {
        int withdrawSelection;

        System.out.println("Withdraw money:");
        System.out.println("1 - $20");
        System.out.println("2 - $40");
        System.out.println("3 - $60");
        System.out.println("4 - $100");
        System.out.println("5 - Back to main menu");
        System.out.print("Choice: ");
        withdrawSelection = input.nextInt();

        switch (withdrawSelection)
        {
        case 1:
            checkNsf(20);
            drawMainMenu();
            break;
        case 2:
            checkNsf(40);
            drawMainMenu();
            break;
        case 3:
            checkNsf(60);
            drawMainMenu();
            break;
        case 4:
            checkNsf(100);
            drawMainMenu();
            break;
        case 5:
            drawMainMenu();
            break;
        }
    }

    public void query()
    {

        Scanner keyboard = new Scanner(System.in);
        double input = keyboard.nextInt();

        if (input == 2)
        {

            BankMainPart2 main2 = new BankMainPart2();

            System.out.println("Please enter your 5 digit card number.");
            BankMainPart2.loginCard(cardNum);

        }
        else if (input == 1)
        {

            cardNumbers();

        }

        else if (input == 3)
        {
            System.out.println("Thank you, have a nice day!");
            System.exit(0);

        }

    }

    public void checkingMenu()
    {

        AccountMain main3 = new AccountMain();
        int selection;

        System.out.println("\nATM main menu:");
        System.out.println("1 - View account balance");
        System.out.println("2 - Withdraw funds");
        System.out.println("3 - Add funds");
        System.out.println("4 - Back to Account Menu");
        System.out.println("5 - Terminate transaction");
        System.out.print("Choice: ");
        selection = input.nextInt();

        switch (selection)
        {
        case 1:
            viewAccountInfo2();
            break;
        case 2:
            withdraw();
            break;
        case 3:
            addFunds();
            break;
        case 4:
            AccountMain.selectAccount();
            break;
        case 5:
            System.out.println("Thank you for using this ATM!!! goodbye");
        }
    }

    private static void checkNumber() throws invalidNumber // run the check activation exception
    {
        if (String.valueOf(input).length() != 5)
        {
            throw new invalidNumber("invalid number");
        }
        else
        {

            System.out.println("Works!");
        }

    }

    public static void main(String args[])
    {
        BankMain myAtm = new BankMain();
        myAtm.startAtm();
    }
}

Answer 1

Why you are having three different instances of Scanner class.. That is what making the program confusing..

In the compareNumber() method, you are actually checking the value of input, which is an instance of Scanner.. It’s better to use it like this: –

checkNumber(input.nextInt())

And add the number to the list in your checkNumber(int num) method..

Of course I am not saying that it is a good way of coding.. But it will solve your problem for the time being..

Else, there are so many issues with your code..

This is your try-catch block: –

        try {
            System.out.println("Please select a 5 digit card number");
            cardNum.add(input.nextInt());
            checkNumber();
        } catch (invalidNumber err) {
            System.out.println("Caught Error: " + err.getError());
        }

And this is your checkNumber() method : –

private static void checkNumber() throws invalidNumber 
{
    if (String.valueOf(input).length() != 5) {
        throw new invalidNumber("invalid number");
    }
    else {
        System.out.println("Works!");
    }
}

Now you must see that you are using input as a parameter to String.valueOf(input).

But you have declared ‘input` as an instance of Scanner before your try-catch block..

    Scanner cards = new Scanner(System.in);
    Scanner input = new Scanner(System.in);
    Scanner keyboard = new Scanner(System.in);

This code is in your codeNumbers() method..

So, clearly your input can never actually contain a user input, rather a hashcode representing the object new Scanner(System.in).

So, its better that you pass the integer input from user to checkNumber() method..

************ MODIFICATION Needed in Code..

So, your checkNumber()` will be modified as: –

    private static void checkNumber(int number) throws invalidNumber 
    {
        if (String.valueOf(number).length() != 5) {
            throw new invalidNumber("invalid number");
        }
        else {
            System.out.println("Works!");
        }
    }

And your call to this method in try-catch block will change to this: –

        try {
            System.out.println("Please select a 5 digit card number");
            int number = input.nextInt();
            cardNum.add(number);
            checkNumber(number);
        } catch (invalidNumber err) {
            System.out.println("Caught Error: " + err.getError());
        }