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how to write while loop

I am currently making a simple ATM program in java.
I want to write a while loop where when user enters wrong pin it will prompt the user to enter again until the pin is matched. When the pin is matched, it will display the main menu.
I tried by myself, but I don't know how to fix it.
while(userPIN != savedPIN)
{
System.out.print("Please enter your correct PIN : ");
Scanner again = new Scanner(System.in);
int pass = again.nextInt();
break;
}

Remove the `break;' statement and update userPIN with the new pin as follows:
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
int savedPIN = 4444;
Scanner input = new Scanner(System.in);
System.out.println("Enter password");
int userPIN = input.nextInt();
double withdraw = 0.0, amount = 0.0, deposit = 0.0;
while (userPIN != savedPIN) {
System.out.print("Please enter your correct PIN : ");
Scanner again = new Scanner(System.in);
userPIN = again.nextInt();
}
while (userPIN == savedPIN) {
System.out.println(" 1 - Inquire Balance \n 2 - Withdraw \n 3 - Deposit \n 0 - Quit ");
Scanner inputNum = new Scanner(System.in);
int number = inputNum.nextInt();
switch (number) {
case 1:
System.out.println("The current balance is $" + amount);
break;
case 2:
System.out.println("Enter the amount to withdraw : ");
withdraw = input.nextDouble();
if (amount >= withdraw) {
amount = amount - withdraw;
System.out.println("The current balance is $" + amount);
} else {
System.out.println("Insufficient balance");
}
break;
case 3:
System.out.println("Enter the amount to deposit : ");
deposit = input.nextDouble();
amount = amount + deposit;
System.out.println("The current balance is $" + amount);
break;
case 0:
System.exit(4);
}
}
}
}

Ok 2 errors:
1)you test userPIN != savedPIN but you accept the value into variable pass with which you do nothing.
2)remove the break in the first loop it will always exit without looping.
it should look like :
while(pass!= savedPIN)
{
System.out.print("Please enter your correct PIN : ");
Scanner again = new Scanner(System.in);
int pass = again.nextInt();
}

(JAVA) do while loop for my vending machine

this project i use do while loop with switch case to check the input case is not match or not. i run the code but the result not what i wanted. what i expect is if the user type the wrong case, the do while loop will loop back to the input where user need to enter the case.
here is the code
package vending.machine;
import java.util.Scanner;
import java.util.*;
import java.util.ArrayList;
import static vending.machine.adddrinks.drinksList;
public class VendingMachine {
public static void main (String []args){
Scanner sc= new Scanner(System.in);
double money;
double total;
double balance;
do{
System.out.println("\nPlease insert money:");
money = sc.nextDouble();
if(money < 1.2){
System.out.println("Not enough money");
}
}while(money < 1.2);
System.out.println("What drinks are you looking for");
adddrinks.showDrinks();
adddrinks.viewDrinks();
System.out.print("Select: 1 or 2 or 3 or 4\n");
int select=sc.nextInt();
do{
switch(select){
case 1:{
total = adddrinks.drinksList.get(0).getdrinkPrice();
balance = money - total;
System.out.println("Here is your balance: " + balance);
break;
}
case 2:{
total = adddrinks.drinksList.get(1).getdrinkPrice();
balance = money - total;
System.out.println("Here is your balance: " + balance);
break;
}
case 3:{
total = adddrinks.drinksList.get(2).getdrinkPrice();
balance = money - total;
System.out.println("Here is your balance: " + balance);
break;
}
case 4:{
total = adddrinks.drinksList.get(3).getdrinkPrice();
balance = money - total;
System.out.println("Here is your balance: " + balance);
break;
}
default:{
System.out.println("Invalid");
break;
}
}
}while(select<5);
}
}
here is the result
enter image description here

From what I understood from your code. When you are giving the input as 5 it is giving invalid.
After that it will go to the while statement and check the condition there. If you are inside the switch case and select any random case It will show you invalid. After that depending upon the number that you have entered.
If the number is less than 5, It will again go to switch case.
As it doesn't make sense as If you continue to provide correct input to it. The code will continue to execute making the balance going in the negative. this condition should be changed to
while(balance>1.2)
assuming that it is minimum amount that is necessary to buy a drink. This will check the condition after every drink and will hopefully do what you were hoping.
On side Note : Make your code modular.

You need to loop over your input, i was so free to improve your code a bit (sorry I do not like repetations):
private static void main10(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("What drinks are you looking for");
adddrinks.showDrinks();
adddrinks.viewDrinks();
int select = 0;
double balance = 0;
boolean running = true;
while (running) {
if (sc.hasNextInt()) {
select = sc.nextInt();
if (0 < select && select <= adddrinks.drinksList.size()) {
double price = adddrinks.drinksList.get(select - 1).getdrinkPrice();
if (balance < price) {
System.out.println("Not enough money, " + select + " costs " + price);
} else {
balance -= price;
System.out.println("You choosed " + select + " , you will find it in the dispenser");
}
} else {
System.out.println("Invalid input, please retry");
}
} else if (sc.hasNextDouble()) {
balance += sc.nextDouble();
} else {
String input = sc.next();
if (input == "q") {
running = false;
if (0 < balance)
System.out.println("please don't forget your change with amount of: " + balance);
System.out.println("Have a nice day, happy to see you again");
break;
} else if (input == "h") {
System.out.println("What drinks are you looking for");
adddrinks.showDrinks();
adddrinks.viewDrinks();
} else {
System.out.println("Invalid input, please retry");
}
}
System.out.println("Your balance is: " + balance);
System.out.println(
"please chouce your product (e.g 2), enter coins (e.g 2.0), click on 'h' to show product list or click on 'q' to get your change");
}
}

How to write a go back code so after the user selects a case he/she can go back to the last option?

package thecashmachin;
import java.util.Scanner;
public class TheCashMachin {
public static void main(String[] args) {
int pin, proceed2=0, withdraw, dailydraw, Proceed, proceed3 = 0;
double balance;
Scanner pinnumber = new Scanner(System.in);
Scanner proc2 = new Scanner(System.in);
Scanner withd = new Scanner(System.in);
Scanner Next = new Scanner(System.in);
Scanner proc3 = new Scanner(System.in);
balance = 9999.99;
dailydraw = 1000;
System.out.println(
"text .");
System.out.println("1)Proceed");
System.out.println("2)Return Card");
Proceed = Next.nextInt();
switch (Proceed) {
case 1:// Proceed
System.out.println("Please enter your 5 digit pin below.");
Scanner Pin = new Scanner(System.in);
int Pincode = Pin.nextInt();
if (Pincode > 9999 && Pincode < 99999) {
System.out.println("1)Display Balance");
System.out.println("2)Withdraw Cash");
System.out.println("3)Other services");
proceed2 = proc2.nextInt();
} else {
System.err.println(
"text");
}
break;
case 2:// Return Card
System.err.println("text");
break;
default:
System.err.println(
"text");
break;}
switch (proceed2) {
case 1:
System.out.println("Your balance today is: 9999.99");
/*
* so right here the balance is shown and in real life you would have a go back button to display the other options but on my code after the balance is displayed you cant do anything else have to re run the the script i want a code that if selected goes back to the last option*/
break;
case 2:
System.out.println("Amount to withdraw");
withdraw = withd.nextInt();
System.out.println("Please take the cash");
System.out.println("Current Balance" + " " + (balance - withdraw));
System.out.println("Daily withdraw left:" + (dailydraw - withdraw));
if (withdraw > dailydraw) {
System.err.println("text");
}
case 3:
System.out.println("Would you like to;");
System.out.println("1)Order a check");
System.out.println("2)Order a Statement");
proceed3 = proc3.nextInt();
break;
default:
System.out.println("text");
}
switch (proceed3) {
case 1:
System.out.println("Your check has been orderd");
break;
case 2:
System.out.println("Your Statement has been orderd");
break;
}
}
}

DO
BOOLEAN = TRUE;
SWITCH() // WITH THE DIFFERENT CASES
DEFAULT BOOLEAN = FALSE;
WHILE BOOLEAN IS FALSE;
This should do. Use a simple do while loop.
Before entering the switch, your boolean is set to TRUE and if it comes to the default it turns it to FALSE and you loop until the boolean stays TRUE

An easy way I know is just making a Boolean before which is kept same as default..
boolean test = True;
while (test)
{
switch(Proceed)
{
case 1://Proceed
System.out.println("Please enter your 5 digit pin below.");
Scanner Pin=new Scanner(System.in);
int Pincode=Pin.nextInt();
test = false;
break;
case 2://Return Card
System.err.println("Your card is being ejected.\n Please Wait..");
test = false;
break;
default:
System.err.println("Sorry your request could not be processed.\n Please enter the pin again.\n")
// when neither case is true, keeps loop running.
break;
}
}

Validate Scanner input on a numeric range

I'm currently creating my first game which is executed in a console.
I've been asked to validate an input which can be done with a simple code. The goal is to input, and then validate if that number is an integer, and is on a range of 1-4. If possible, the problem should be solved with basic algorithm.
The problem is that it won't give me the result I wanted. It works when I enter a string, but it loops on every number I put including the number in the range. Does anyone know why?
public class Menu {
public static void main(String[] args) {
try (Scanner scanner = new Scanner(System.in)) {
int input = 0;
int min = 1;
int max = 4;
boolean inputValidate;
System.out.println("Main Menu");
System.out.println("=========");
System.out.println("1. Play Game");
System.out.println("2. About");
System.out.println("3. View Saved Games");
System.out.println("4. Exit");
System.out.println("");
do {
System.out.print(">> ");
if (!scanner.hasNextInt()) {
inputValidate = false;
System.out.println("Not a number. Please input number 1-4.");
scanner.nextLine();
} else if (input <= max && !(input < min)) // if input <= 4 and input is not less than 1
{
input = scanner.nextInt();
inputValidate = true;
} else {
inputValidate = false;
System.out.println("Not in range. Please input number 1-4.");
scanner.nextLine();
}
} while (!(inputValidate));
switch (input) {
case 1:
break;
case 2:
System.out.println("Good work!");
break;
case 3:
break;
case 4:
break;
}
}
}
}

Because you instantiate input to be 0, but never give the user an opportunity to change this, the conditions for the first two conditionals are always false (nothing is read from the Scanner and 0 is not between min and max). Therefore, the program falls through to the else every time. Just add a statement before the do-while that will obtain a value for input from the user.
input = scanner.nextInt();
// your do-while loop
(You'll also probably have to adjust the code slightly to get the type of interaction you're looking for. Hint - you're reading two values from the user.)

As Clint said the problem was in your input. Here's a demo how you can fix this,
try (Scanner scanner = new Scanner(System.in)) {
int input = 0;
int min = 1;
int max = 4;
boolean inputValidate = false;
System.out.println("Main Menu");
System.out.println("=========");
System.out.println("1. Play Game");
System.out.println("2. About");
System.out.println("3. View Saved Games");
System.out.println("4. Exit");
System.out.println("");
do {
System.out.print(">> ");
try {
input = scanner.nextInt();
if (input >= min && input <= max) {
inputValidate = true;
} else {
System.out
.println("Not in range. Please input number 1-4.");
scanner.nextLine();
}
} catch (InputMismatchException exception) {
System.out
.println("Not a number. Please input number 1-4.");
scanner.nextLine();
}
} while (!(inputValidate));

Java - Running totals(using do while and if else statements)

I'm not very adept in getting the running totals using Java as I've started recently. I have to display and hold the running total of the bank balance and for some strange reason, it's resetting back to 100, which is what I declared it as to start with. Is there any way for me to stop the bank balance from being reset every time it loops?
public static void main(String args[])
{
Scanner sc = new Scanner(System.in);
int choice, totBal = 0, totWith = 0, totDep = 0;
double with, remBal = 0, deposit, bankBal = 100;
char reply = 0;
do
{
System.out.println("");
System.out.println("Bank online\n");
System.out.println("1. Withdraw");
System.out.println("2. Deposit");
System.out.println("3. Balance");
System.out.println("4. Account Details");
System.out.println("5. Exit\n");
System.out.print("Enter your choice: ");
choice = sc.nextInt();
if(choice == 1)
{
System.out.print("How much do you wish to withdraw?\n");
with = sc.nextInt();
remBal = bankBal - with;
System.out.println("Your new balance is: " + remBal);
totWith++;
}
else if(choice == 2)
{
System.out.print("How much do you wish to deposit?\n");
deposit = sc.nextInt();
remBal = remBal + deposit;
System.out.println("Your new balance is: " + remBal);
totDep++;
}
else if(choice == 3)
{
System.out.println("Your balance is: " + remBal);
totBal++;
}
else if(choice == 4)
{
System.out.println("You made " + totWith + " withdrawls from your account.");
System.out.println("You made " + totDep + " deposits to your account.");
System.out.println("You made " + totBal + " balance checks on your account.");
}
else if(choice == 5)
{
}
System.out.println("");
System.out.print("Do you want to enter another option?(y/n): ");
reply = sc.next().charAt(0);
}while(reply == 'Y' || reply == 'y');
System.out.println("Thank you and goodbye!");
}
}
Also, I feel that I have WAY too many variables. How can I cut back on these?

Your problem is with following statement:
double with, remBal = 0, deposit, bankBal = 100;
Here you are initialising remBal as 0, while when one deposits amount/checks balance you do:
remBal = remBal + deposit;//you use remBal for blaance check
So on first attempt it will try to add 0 with say $100 which will be 100 while bankBal is 100 it should be 100. So initialize remBal same as bankBal (or use just one variable for bankBalance i.e. either of one).

You set the bankBal value to 100 at the start of the program.
When doing withdrawals, you always do
remBal = bankBal - with
which will always equate to
remBal = 100 - with
since you never change bankBal to reflect the updated balance after each loop.
One approach to solve this is to remove the
bankBal
variable altogether and simply set your
remBal
variable to your desired starting value.
Finally change the withdrawal computation mentioned above to
remBal = remBal - with

One thing you can do is implement switch-cases to call methods specific to Depost, Withdraw, etc. An example of this roughly would be:
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Please Enter what you would like to do: ");
String enterPrompt = input.next();
int options = 5;
switch (options) {
case 1: enterPrompt = "Deposit";
doDeposit();
break;
case 2: enterPrompt = "Withdrawel";
doWithdrawel();
break;
case 3: enterPrompt = "Balance";
viewBalance();
break;
case 4: enterPrompt = "Account Details";
viewAccount();
break;
case 5: enterPrompt = "Exit";
System.exit(1);
break;
}
public void doDeposit(){
//local variables here
//Do stuff
}
public void doWithdrawel(){
//local variables here
//Do stuff
}
public void viewBalance(){
//local variables here
//Do stuff
}
public void viewAccount(){
//local variables here
//Do stuff
}
}