Writing for loops/while loops?

Question

I'm in a programming class in high-school, and I was given an assignment to make a basic subtotal and top calculator, but I work at a restaurant, so it seemed a little pointless to make a calculator that only let you read in one food. So I tried to make it able to take in multiple food items and add them to one price variable. Sorry if some of this code may seem inefficient or redundant. It's only high-school of course.

The issue is, when I run it, it gets up to the asking if there was another food item the user would like to add, and when I type in "Yes" or "No", the program does nothing. Keeps running, but goes no further. Any explanations?

import java.text.NumberFormat;
import java.util.Scanner;

public class Price {

    /**
     * @param args
     */
    public static void main(String[] args) {

        final double taxRate = .0887; //8.87% Tax Rate
        double tipRate;
        int quantity1;
        Scanner kb = new Scanner(System.in);
        double subtotal, tax, tip, totalCost1, unitPrice1 = 0;
        String done;

        System.out.println ("How many of the first item did you get?: ");
        quantity1 = kb.nextInt();

        for (int i = 0; i < quantity1; i++)
        {
        System.out.println ("What was the price of that single item "+(i+1) + ": ");
        unitPrice1 = kb.nextDouble();

        System.out.println ("Was there another food item you'd like to add?: ");
        done=kb.next();
        while (done.equalsIgnoreCase("Yes"));
        }

        System.out.println ("What percent would you like to tip? (Formatted like 0.10 for 10%, 0.20 for 20%, etc.): ");
        tipRate = kb.nextDouble();

        subtotal= quantity1 * unitPrice1;
        tax = subtotal * taxRate;
        totalCost1 = subtotal + tax;
        tip = totalCost1 * tipRate;
        totalCost1 = totalCost1 + tip;


        //Formatting
        NumberFormat money = NumberFormat.getCurrencyInstance();
        NumberFormat tipMoney = NumberFormat.getCurrencyInstance();
        NumberFormat taxPercent = NumberFormat.getPercentInstance();
        NumberFormat tipPercent = NumberFormat.getPercentInstance();


        System.out.println ("Your total before tax is: " + money.format(subtotal));
        System.out.println ("The tax is " + money.format(tax) + " at " + tipPercent.format(taxRate));
        System.out.println ("The tip at " + tipPercent.format(tipRate) + " is " + tipMoney.format(tip));

    }

}

Answer 1

You're while loop is doing nothing, you had given it a condition, but it has no instruction.

Try something like this..(sorry for my rusty java)

'public static void main(String[] args) {

//variable declaration
bool running = true

final double taxRate = .0887; //8.87% Tax Rate
double tipRate;
int quantity1;
Scanner kb = new Scanner(System.in);
double subtotal, tax, tip, totalCost1, unitPrice1 = 0;
String done;

while(running = true){
    System.out.println ("How many of the first item did you get?: ");
    quantity1 = kb.nextInt();

    for (int i = 0; i < quantity1; i++)
    {
    System.out.println ("What was the price of that single item "+(i+1) + ": ");
    unitPrice1 = kb.nextDouble();

    System.out.println ("Was there another food item you'd like to add?: ");
    done=kb.next();

        if(done.equalsIgnoreCase("No")){
            running = false
        //Allows you to break out of the while loop if the user does not want to add anything else
        //DO NOT USE BREAK STATMENTS, IT IS A POOR PROGRAMMING PRACTICE.
        };//end if
    }//end for
}//end while

    System.out.println ("What percent would you like to tip? (Formatted like 0.10 for 10%, 0.20 for 20%, etc.): ");
    tipRate = kb.nextDouble();

    //You should comment whats going on here
    subtotal= quantity1 * unitPrice1;
    tax = subtotal * taxRate;
    totalCost1 = subtotal + tax;
    tip = totalCost1 * tipRate;
    totalCost1 = totalCost1 + tip;

    //Formatting
    NumberFormat money = NumberFormat.getCurrencyInstance();
    NumberFormat tipMoney = NumberFormat.getCurrencyInstance();
    NumberFormat taxPercent = NumberFormat.getPercentInstance();
    NumberFormat tipPercent = NumberFormat.getPercentInstance();

    //Output
    System.out.println ("Your total before tax is: " + money.format(subtotal));
    System.out.println ("The tax is " + money.format(tax) + " at " + tipPercent.format(taxRate));
    System.out.println ("The tip at " + tipPercent.format(tipRate) + " is " + tipMoney.format(tip));

}//end main

Answer 2

You have an infinite loop here:

while (done.equalsIgnoreCase("Yes"));

Once you enter Yes, it will keep sitting there and doing nothing because the value of done is Yes and never changes.

Also your loop structure is a bit odd. Your outer for loop runs as many times as the quantity of the first item. But shouldn't you only be multiplying that number to the cost? Because you are either running the loop for as long as the number of items the user entered (by asking them up front) or you don't ask them the total number of items and simply ask them to enter Yes if they want to add more items; you can't really do both.

Your loop should probably look something like this:

String input = "Yes";
while(input.equalsIgnoreCase("Yes")) {
    System.out.println ("How many of the first item did you get? ");
    quantity1 = kb.nextInt();

    System.out.println ("What was the price of that single item? ");
    unitPrice1 = kb.nextDouble();

    //total += unitPrice1 * quantity1 - you don't have this in your code, but this is where you would be calculating the running total

    System.out.println("Was there another food item you'd like to add? ");
    input = kb.next();
}

Answer 3

you need to exit for loop when user enters yes, so you can use label here like below:

  outerloop:
  for (int i = 0; i < quantity1; i++)
            {
            System.out.println ("What was the price of that single item "+(i+1) + ": ");
            unitPrice1 = kb.nextDouble();

            System.out.println ("Was there another food item you'd like to add?: ");
            done=kb.next();
            while (done.equalsIgnoreCase("Yes")){
                     break outerloop;
               }
            }

Your current code does not do anything inside the while loop if you don't enter yes. And if you enter yes it will be stuck in infinite loop because of your while loop. This is not the efficeint way of looping, but this code will have least change in your current code.