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How to create a java code for calculating the menu prices using if else and while loop

I need to create a code using java.
When any person enters this beverage shop, it shows how to select and order the menu items and quantity. After selecting one menu, code asks "Do you want to select another menu item". If you don't want another menu enter (-1). After entering (-1) price calculate through the code.The balance is over 1000/= the shop gives 10% discount. The service charge(20%) and VAT(12%) must be added to the balance.
I have created a java code but it does not stop when user enter(-1) and I selected any one menu with one quantity, it shows the balance is 0.0
What is the error of my code.
Scanner scan=new Scanner(System.in);
int i=0;
double tot=0,price,vat,service,res=0,result;
System.out.println("\t\t\t\tWELCOME TO BEVERAGE SHOP");
System.out.print("User Name:");
String name=scan.next();
System.out.println("Hello!!!"+" "+name+" "+"Welcome...");
System.out.print("\n");
System.out.println("Please see our menu and select");
System.out.print("\n");
System.out.println("|\tPRODUCT ID\t|\t\tPRODUCT NAME\t\t|\tPRICE(LKR)\t|\n|\t1\t\t|\t\tTea\t\t\t|\t80\t\t|\n|\t2\t\t|\t\tCoffee\t\t\t|\t100\t\t|\n|\t3\t\t|\t\tIce Coffee\t\t|\t150\t\t|");
System.out.print("\n");
System.out.println("If you have selected the items you want,you can enter the product below");
while(i>=0){
System.out.print("Product Id:");
int id=scan.nextInt();
System.out.print("Qyantity:");
double quan=scan.nextDouble();
System.out.println(id +":"+quan);
System.out.print("if you want to stop entering id and buy, please enter \"(-1)\" \nor you want to continue enter anothe number:");
int no=scan.nextInt();
if(no==-1){
vat=(res*12)/100;
service=(res*20)/100;
result=vat+service;
System.out.println("Your Amount is:"+" "+result);
if(res>1000){
price=(res*10)/100;
vat=(res*12)/100;
service=(res*20)/100;
result=(vat+service)-price;
System.out.println("Your Amount is:"+" "+result);
}
}
else{
switch(id){
case 1:
tot=80*quan;
break;
case 2:
tot=100*quan;
break;
case 3:
tot=150*quan;
break;
}
res+=tot;
}
}
i++;
}
}

while(i>=0){
This line checks whether you'll continue or not. It only checks i.
i++;
this is the only line where I see you alter the value of i. Now, in order to get to that line, i has to be > 0.
Guess what (i+1) > 0 will return?
There's your endless loop.
You'll need to change
i++;
into i= scan.nextInt();
or check other variables.

I will shorten this:
int no=scan.nextInt();
while(i>=0){
//your code
int no=scan.nextInt();
if(no==-1){
//your code
// leave the loop
break;
}
}
you need for the exit / break condition and then leave the while - loop

How do I keep track of the balance on a bank account?

I am going to create a program that keeps track of the balance on a bank account. The program shall use a loop that continues until the user choses to exit by answering no to the question Do you want to continue?.
In the loop the user shall be asked to enter an amount (positive for deposit and negative for withdraw). The amount shall be added/subtracted from an account balance variable. All deposits/withdraws shall be saved as a history so that we can print it later. When the user choses to exit the loop the current account balance together with the account history (from the array/ArrayList) shall be printed.
Now, I want to use an array with ten slots for the history feature.
My question is how can I keep track of the all deposit, withdraw and current account balance (using an array with ten slots for the history feature) so that I can print it out while the user exits the program?
My code:
BankApp class:
package bankapp;
import java.util.Scanner;
public class BankApp {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
askingUser au = new askingUser();
System.out.println("WELCOME TO OUR BANK!\nYou have 100 SEK by default in your account.");
while (true) {
au.userInput();
System.out.println("Do you want to continue? Answer by Yes or No.");
String yesOrNo = input.next();
if (yesOrNo.equalsIgnoreCase("yes")) {
au.userInput();
} else if (yesOrNo.equalsIgnoreCase("no")) {
System.out.println("History: ");
//print out the transaction history
System.exit(0);
} else {
System.out.println("Invalid character input.");
}
}
}
}
askingUser class:
package bankapp;
import java.util.Scanner;
public class askingUser {
Scanner input = new Scanner(System.in);
double initialBal = 100;
public void userInput() {
System.out.println("Enter your amount: (+ve for deposit & -ve for withdraw)");
double inputAmount = input.nextDouble();
if (inputAmount >= 0) {
double newPosAm = initialBal + inputAmount;
System.out.println("Your current balance is: " + newPosAm + " SEK");
} else {
double newNegAm = initialBal + inputAmount;
System.out.println("Your current balace is: " + newNegAm + " SEK");
}
}
}

If you use an array, you have to keep track of the number of elements stored inside and resize the array when necessary. The easiest way would be to keep the history as strings in ArrayList. You would add one message to that list per transaction:
ArrayList<String> history = new ArrayList<String>();
void addToHistory(String transaction) {
history.add(transaction);
}
void printHistory() {
for(String s : history) {
System.out.println(s);
}
}
addToHistory("Withdrawal: 100 SEK" );
addToHistory("Deposit: 200 SEK" );
printHistory();

You need a queue to do that. However, for a simple, fast and primitive implementation you can:
Define an object called Transaction(deposit - double, withdraw - double, current account balance - double)
Add a List of Transactions into askingUser class as an attribute. I strongly recommend renaming the class name to AskingUser to make it seen as object.
At each operation add a new Transaction to end of the List you just added.
At exit, print out the last -say- 10 elements of the List; you can reach it through askingUser object. You can also define a function in askingUser class to print out the last 10 elements, if you make the function work according to selected number of elements, you can add number of Transactions to the function's inputs.

Java Menu going into an infinite loop

i'm getting an infinite loop with the program i'm doing and i'm not sure how to get passed it. been working at this a few hours and i cant figure it out. (sorry if this seems very simple to you guys, but i'm still new at java). basically what is happening is that everything compiles and works as it should at first, but as soon as i enter a selection it repeats the main menu WITHOUT giving me the intended operation.
for example, the program should work to where i enter "1, 2, 3, or 4" as a selection and it displays "Good morning" in English, Italian, Spanish, and German respectively and 5 ends the program. what happens instead is that the menu repeats itself if i enter 1, 2, 3, 4, or 5 as a selection.
entering any number other than 1-5 displays an error message saying that the selection is invalid, as it should. so that while loop works as intended. so can anyone point out what i did wrong?
import java.util.Scanner;
import java.io.*;
public class Translator
{
public static void main(String[] args)
{
// local variable to hold the menu selection
int selection = 0;
do
{
// display the menu
displayMenu(selection);
// perform the selected operation
switch (selection)
{
case 1:
System.out.println("Good Morning.");
break;
case 2:
System.out.println("Buongiorno.");
break;
case 3:
System.out.println("Buenos dias.");
break;
case 4:
System.out.println("Guten morgen.");
break;
case 5:
System.out.println("GoodBye!");
break;
}
} while (selection != 5);
}
// the displayMenu module displays the menu and gets and validates
// the users selection.
public static void displayMenu(int selection)
{
//keyboard scanner
Scanner keyboard = new Scanner(System.in);
// display the menu
System.out.println(" select a language and i will say good morning");
System.out.println("1. English.");
System.out.println("2. Italian.");
System.out.println("3. Spanish.");
System.out.println("4. German.");
System.out.println("5. End the Program.");
System.out.println("Enter your selection");
// users selection
selection = keyboard.nextInt();
while (selection < 1 || selection > 5)
{
System.out.println ("that is an invalid select.");
System.out.println (" Enter 1, 2, 3, 4, or 5.");
selection = keyboard.nextInt();
}
}
}

The problem is that arguments to methods are passed by value in Java. So the part at the end of displayMenu where you set a new value for the selection parameter doesn't change the value of the selection local variable in main at all. So in main, the selection variable always has the value of 0.
Given that you're not using the original value of selection in displayMenu, you should just turn it into a method with no parameters, but which returns the selected value:
public static int displayMenu()
{
// Code to print out the menu [...]
int selection = keyboard.nextInt();
while (selection < 1 || selection > 5)
{
System.out.println ("that is an invalid select.");
System.out.println (" Enter 1, 2, 3, 4, or 5.");
selection = keyboard.nextInt();
}
return selection;
}
And in main:
int selection;
do
{
selection = displayMenu();
switch (selection)
{
...
}
}
while (selection != 5);

Java doesn't support "true" pass-by-reference, which is what your program seems to rely on. You initialize a variable to 0 and ask a method to change it, which can't happen. The parameter values you have inside methods are mere copies of the original values passed to them. A small demonstration: consider you have this method...
public static void increment(int a) {
a++;
}
and a code that uses it...
int a = 0;
increment(a);
System.out.println(a);
0 is printed, because the only thing that's incremented is the local copy of a in the method increment. The original value stays unchanged.
You could make your method instead return a value as suggested in Jon Skeet's answer.

the simplest solution when you stuck in a program is that use debug tools.
begug tools that exist in every compiler like eclipse or netbeans not only in this program but also in any program can help you.
then come back to your project and use this tools. you can find your wrong.
good luck!!

You call displayMenu() within the do-while loop and there is a problem with passing values between methods. And yes there is problem with your indentation. Check topics like control statements, variables in a book. An improved version is shown below:
package imporvedtranslator;
import java.io.*;
import java.util.Scanner;
public class ImporvedTranslator
{
public static void main(String[] args)
{
int selection;
selection = displayMenu();
switch (selection)
{
case 1:
System.out.println("Good Morning.");
break;
case 2:
System.out.println("Buongiorno.");
break;
case 3:
System.out.println("Buenos dias.");
break;
case 4:
System.out.println("Guten morgen.");
break;
case 5:
System.out.println("GoodBye!");
break;
}
}
private static int displayMenu()
{
int sel;
Scanner sc = new Scanner(System.in);
System.out.println(" select a language and i will say good morning");
System.out.println("1. English.");
System.out.println("2. Italian.");
System.out.println("3. Spanish.");
System.out.println("4. German.");
System.out.println("5. End the Program.");
System.out.println("Enter your selection");
sel = sc.nextInt();
while (sel<1 || sel>5)
{
System.out.println ("that is an invalid select.");
System.out.println (" Enter 1, 2, 3, 4, or 5.");
sel = sc.nextInt();
}
return sel;
}
}

Do while Loop to show a menu

I have created my menu with do~while(true); but every time the user insert a number, instead of running the program it shows the the menu again! what do you think?
// my main method
public static void main(String[] args) {
DataReader reader = new DataReader(); // The reader is used to read data from a file
// Load data from the file
if(reader.loadData(args[0])) { // The filename is entered using a command-line argument
vehicles= reader.getVehicleData(); // Store the arrays of Vehicle
// Display how many shapes were read from the file
System.out.println("Successfully loaded " + vehicles[0].getCount() +
" vehicles from the selected data file!");
displayMenu();
}
}
// dispaly menu method
private static void displayMenu() {
Scanner input = new Scanner(System.in);
do {
System.out.println("\n\n Car Sales Menu");
System.out.println("--------------------------------------");
System.out.println("1 - Sort vehicles by owner's Last Name");
System.out.println("2 - Sort vehicles by vehicle Model");
System.out.println("3 - Sort vehicles by vehicle Cost\n");
System.out.println("4 - List All Vehicles");
System.out.println("5 - List All Cars");
System.out.println("6 - List American Cars Only (Formal)");
System.out.println("7 - List Foreign Cars only (Formal)");
System.out.println("8 - List All Trucks");
System.out.println("9 - List All Bicycles");
System.out.print("\nSelect a Menu Option: ");
getInput(input.next()); // Get user input from the keyboard
}
while(true); // Display the menu until the user closes the program
}
// getInput method
private static void getInput(String input) {
switch(Convert.toInteger(input)) {
case 1: // Sort Vehicles by Owner's Last Name
Array.sortByOwnerName(vehicles);
break;
case 2: // Sort Vehicles by Vehicle Make & Model
Array.sortByVehicleMakeModel(vehicles);
break;
case 3: // Sort Vehicles by Vehicle Cost
Array.sortByVehicleCost(vehicles);
break;
case 4: // List All Vehicles
displayVehicleData(0);
break;
default:
System.out.print("The entered value is unrecognized!");
break;
}
}

Because you have while(true);, this means that the menu it will be in a infinite loop until a break is call.
Try to do something like:
do {
System.out.println("\n\n Car Sales Menu");
System.out.println("--------------------------------------");
System.out.println("1 - Sort vehicles by owner's Last Name");
System.out.println("2 - Sort vehicles by vehicle Model");
System.out.println("3 - Sort vehicles by vehicle Cost\n");
System.out.println("4 - List All Vehicles");
System.out.println("5 - List All Cars");
System.out.println("6 - List American Cars Only (Formal)");
System.out.println("7 - List Foreign Cars only (Formal)");
System.out.println("8 - List All Trucks");
System.out.println("9 - List All Bicycles");
System.out.print("\nSelect a Menu Option: ");
try {
int input = Integer.parseInt(getInput(input.next())); // Get user input from the keyboard
switch (input) {
case 1: // do something
break;
case 2: // do something
break;
...
}
} catch (NumberFormatException e) { ... }
}
while(true); // Display the menu until the user closes the program
You can use switch to process the input, and depending on input do the respective action.

while(true); // Display the menu until the user closes the program
while true doesn't mean exactly the thing that you have written in comment. You need to add some other condition in your while loop to check that condition. That condition should be on the input you read from the user.
For e.g, something like this. Note that this might not completely solve your problem, as there seems to be some other issues also with your code: -
int userInput = 0;
do {
try {
userInput = Integer.parseInt(getInput(input.next()));
} catch (NumberFormatException e) {
userInput = 0;
}
} while (userInput < 1 || userInput > 9);
return userInput; // For this you need to change return type of `displayMenu()`
And then, process the userInput returned in your main() method. There you would need to store the return value in some local variable.
int userInput = displayMenu();

Because your while loop is while(true) it will always keep looping until the program is forcefully broken. Without the content of your getInput() function, all that can be said is that the loop will never end.
You will need to handle your user's input, either in the getInput() method or after using it, and then conditionally break out of the while(true) when certain criteria are met.

Assuming your getInput method does what it says it does, you haven't actually done anything with your input once it has been read in.
So when the user enters a value, your program reads the value, happily ignores it, and then runs the menu again.

Find the errors in the BankMenu method

The method bankTellerMenu() is intended to show a bank teller menu and repeatedly obtain the user’s selection and execute that selection. The menu is only redisplayed if an invalid choice is made by the user. There are syntax and logical errors in the method. If these errors were corrected then the actual output would match that displayed below.
Correct the code and test it by producing the output below. I have underlined user responses to make them stand out.
------------------------- Expected output --------------------------
FIT Bank
Deposit
Withdraw
Client Menu
Account Menu
Exit
Select an option (1-5): 7
FIT Bank
Deposit
Withdraw
Client Menu
Account Menu
Exit
Option must be only 1-5
Select an option (1-5): 2
* Invoke withdraw()
Select another option (1-5): 5
------------------------- Expected output --------------------------
Now the problem starts now, i have tried out coding the method, but it doesn't seem to be able to invoke withdraw() or any other choices when i input a value that is between 1 and 5. Can someone help please?
import java.util.*;
public class FITBank
{
//There are no errors in the main method.
public static void main(String[] args)
{
//Just run bank teller menu.
bankTellerMenu();
}
public static void bankTellerMenu()
{
Scanner reader = new Scanner(System.in);
int option = 1;
String message = null;
do{
System.out.println("\n\tFIT Bank");
System.out.println("1. Deposit");
System.out.println("2. Withdraw");
System.out.println("3. Client Menu");
System.out.println("4. Account Menu");
System.out.println("5. Exit");
if(message!=null){
System.out.println("\t"+message);
}
System.out.print("Select an option (1-5): ");
option = reader.nextInt();
if(option < 1 || option > 5){
message = new String("Option must be only 1-5");
option=1;
}
}while(option <1 && option > 5);
if(option == 1) {
System.out.println("***\tInvoke deposit()");
}
if(option == 2){
System.out.println("***\tInvoke withdraw()");
}
if(option == 3)
{ System.out.println("***\tInvoke clientMenu()");
}
if(option==4){
System.out.println("***\tInvoke accountMenu()");
}
}
}

First and foremost: are you familiar with the switch statement? If you're not, then I think this would be a perfect time to learn about it.
Now the problem starts now, i have tried out coding the method, but it doesn't seem to be able to invoke withdraw() or any other choices when i input a value that is between 1 and 5.
Without doing your homework: if you want to invoke the withdraw method, you must have a withdraw method to invoke. So where is your withdraw method? Or are you just supposed to print that you're calling the withdraw method without actually calling it?

You are closing your loop to early. Move all the if(option == ...) statements right before
}while(option >=1 && option < 5);. Otherwise this won't work as expected.
Also I would recommend using a switch statement instead of all those if statements.