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Birthday money calculator

My assignment is to create a calculator that can calculate how much is left on a giftcard after purchasing an item, but also making sure not to go over 6 items, or $225, whichever comes first. I know I need another method to do a calculation but i'm not sure what to put in it. This is what I have so far:
I know I will need a for loop for the counter for the items, but I'm really stuck. I posted the actual assignment to give background.
For your birthday, your rich aunt & uncle give you a $225 gift card to
the local mall. They will go shopping with you and will help carry out
your items. The most that each of you can carry is one item in each
hand. Thus, you may purchase a maximum of six items. You will have a
tracker device that computes the number of items you purchase as well
as the amount of money you have spent. After you choose each item, the
tracker prompts you for the price, and then displays the amount of
money you have spent. Then it displays the number of items you may
still choose and the balance on the gift card. The program will not
terminate until you reach 6 items or $225, whichever comes first. The
tracker then will list the total spent & the number of items as well
as the balance on the gift card.
Required:
validate that negative
prices are not entered and that you can’t spend more than the balance
on the gift card. Give the user as many opportunities as needed to
enter a price above 0 or below 225. User should be able to purchase
items costing between one penny and $225, inclusive.
all dollar
amounts should be formatted for currency using the NumberFormat class.
Include at least 1 method in your program.
Be sure to create test cases for all options:
spend the entire dollar amount on fewer than 6 items
purchase 6 items totaling less than the entire dollar amount
spend the entire dollar amount on exactly 6 items
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
double priceItem = 0, totalPrice = 225, currentPrice = 0;
int numItem;
System.out.println("Happy birthday from Auntie and Uncle! \nYou may purchase up to"
+ " 6 items with this gift card of $225.");
for (numItem = 1; numItem <= 6; numItem++) {
System.out.println("Enter the price for item #" + numItem + ": ");
priceItem = input.nextDouble();
while (numItem <= 6 && totalPrice <= 225) {
totalPrice = currentPrice - priceItem;
System.out.println("You may buy this item. You have spent ");
if (currentPrice > totalPrice) {
System.out.println("Item is too expensive. Balance on gift card is " + currentPrice);
}
}
}
}
Whenever I have tried to make a while loop, it is an infinite loop and again I'm not sure which calculation to put in to get it to break.

I don't want to give you the answer as it is something you should solve yourself but I will give a few pointers.
Your use of a while loop here is incorrect, do you really need a while loop?
if(totalPrice <= 225) break;
Perhaps look into the break statement to exit the loop when a certain condition is met, that why you can ensure there are 6 items or less and it is not over 225.
You also need to handle an entry of 0 as it is a penny minimum and you cannot allow them to exceed 225.
priceItem = input.nextDouble();
while(priceItem < 0.01 || priceItem > 225){
System.out.println("Item Price cannot be 0 or greater than 225, please...");
priceItem = input.nextDouble();
}
You also can't allow a value that exceeds the remaining balance, I will let you try and figure out how to do that yourself. What you have done so far isn't bad you just need to break it down a bit more.

This is how I would construct it:
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
double balance = 225.0;
double itemPrice = 0;
int boughtItems = 0;
int maxItems = 6;
System.out.println("Happy birthday from Auntie and Uncle! \nYou may purchase up to"
+ " 6 items with this gift card of $225.");
while(boughtItems < maxItems && balance > 0) {
System.out.print("You have " + balance + "$ on your giftcard. \nEnter the price for item #" + (boughtItems + 1) + ": ");
itemPrice = input.nextDouble();
if(balance - itemPrice > 0.0) {
balance -= itemPrice;
System.out.println("You have bought the Item!\n\n\nYou can carry " + (maxItems - boughtItems - 1) + " more things!\n");
boughtItems++;
} else {
if(balance - itemPrice == 0) {
balance -= itemPrice;
boughtItems++;
System.out.println("\nYou have spent all your money.");
}
else {
System.out.println("You dont have enough money for this Item!\n\n\n");
}
}
}
System.out.println("You bought " + boughtItems + " item/s. " + "Have fun with the stuff!");
}
You can write a buy(double balance, double price) method for example, so you fill in the assignment requirements.
And of course you need to do the rest of the stuff like the number-formatting.

In the while loop, you are doing wrong assignment, that’s why infinite loop.
Assign currentPrice is equal to totalPrice - price for item purchased.

Is it possible to turn this code into a for loop?

I was wondering whether it is possible to turn this code into a for loop. I know that you could loop the text, however, is it possible to do something similar to the variables inputRangeCity1, inputRangeCity2 etc..
System.out.print("Enter maximum cell phone connectivity distance for city 1: ");
double inputRangeCity1 = user_input.nextDouble();
System.out.print("Enter maximum cell phone connectivity distance for city 2: ");
double inputRangeCity2 = user_input.nextDouble();
System.out.print("Enter maximum cell phone connectivity distance for city 3: ");
double inputRangeCity3 = user_input.nextDouble();
System.out.print("Enter maximum cell phone connectivity distance for city 4: ");
double inputRangeCity4 = user_input.nextDouble();

If you declare inputRangeCity1, etc as separate local variables, it is next to impossible to use a loop.
If you declare inputRangeCity1, etc as separate instance (or class) variables, it is possible to use reflection. However, it is not a good solution ... because the code will be more complex, more verbose and fragile.
The best / simplest solution is to use an array rather than separate variables:
double[] inputRangeCities = new double[NOS_CITIES];
and then:
for (int i = 1; i <= inputRangeCities.length; i++) {
System.out.print("Enter maximum cell phone connectivity " +
"distance for city " + i + ": ");
inputRangeCities[i - 1] = user_input.nextDouble();
}
If the number of cities is not known (fixed) at the point where you need to declare the variable, then you should use a List instead. Otherwise, an array is better ... unless there is some other part of the application wthat would benefit from using a list.
If the array / collection approach is not what you need, then consider refactoring like this:
private double readRange(Scanner input, int cityNo) {
System.out.print("Enter maximum cell phone connectivity " +
"distance for city " + i + ": ");
return input.nextDouble();
}
...
double inputRangeCity1 = readRange(user_input, 1);
double inputRangeCity2 = readRange(user_input, 2);
double inputRangeCity3 = readRange(user_input, 3);
double inputRangeCity4 = readRange(user_input, 4);
It is more lines of code ... and I don't like it ... but it is an alternative.

Use a list instead of individual variables.
List<Double> inputRangeCities = new ArrayList<Double>();
for(int i=1; i <= 4; i++)
{
System.out.print("Enter maximum cell phone connectivity distance for city" + i);
inputRangeCities.add(user_input.nextDouble());
}
You can then for example access the value for the first city as inputRangeCities.get(0). Note that the index in a Java list or array always starts at 0.

Displaying array values through object that references other methods not displaying with for loop

Basically, the point of my program is a payroll program for the user to input amount of employees, then with that same amount of employees go through the process of indicating what kind of employee it is, and then proceed to enter information of employee based on type. Right now, I am going one at a time and first starting out with hourly. I managed to get the output I wanted until I end up completing the while loop's condition to go on and output the resulting table but it does not output the results and only outputs the column labels. I decided to use a for loop so that it continues to display until it reaches a number greater than the size. I checked to see if I was using correct formatting for the array[e].method(); but cant seem to catch anything wrong so far.
Could it be a possibility of the parameters not matching or probably a misuse of it?
Thanks in advance.
Scanner in = new Scanner(System.in);
System.out.println("Welcome to the Company's Payroll System!");
System.out.println("Please enter the amount of employees in the company.");
int size = in.nextInt();
Employee [] staff = new Employee [size];
int i = 0;
while (i != staff.length )
{
System.out.println("Enter employee type (Choose Hourly, Salary, or Manager)");
System.out.println("Press 4 to exit.");
String emptype = in.next();
if (emptype.equalsIgnoreCase("Hourly"))
{
System.out.println("First name:");
String first = in.next();
System.out.println("Last name:");
String last = in.next();
System.out.println("Employee ID (7 digits):");
Float identification = in.nextFloat();
System.out.println("Job Title:");
String title = in.next();
System.out.println("Amount employee makes per hour: ");
double hour = in.nextDouble();
staff [i] = new HourlyEmployee(first, last, identification, title, hour);
i++;
}
}
System.out.println("FIRST NAME \t LAST NAME \t ID \t JOB TITLE \t Weekly Salary");
for (int e = 0; e > size; e++)
{
System.out.printf("%5d", staff[e].getfirstName() + staff[e].getlastName() + staff[e].getId() + staff[e].getTitle() + staff[e].weeklyPay() );}
}
}

In the for loop your condition is wrong. It should be:
for (int e=0; e < size; e++)

In Java, is it possible to use some sort of while loop (or anything) to determine the amount of prompts for input?

public static void main (String [] args)
{
// declare variables, capture input
String input, name = JOptionPane.showInputDialog("Please " +
"enter your first and last name.");
double testScore1, testScore2, testScore3, average;
// capture input, cast, and validate input
input = JOptionPane.showInputDialog("What is the score " +
"of your first test?");
testScore1 = Double.parseDouble(input);
while (testScore1 < 1 || testScore1 > 100)
{
input = JOptionPane.showInputDialog("This test score is not " +
"between 1 and 100. \nPlease enter a test score in " +
"this range:");
testScore1 = Double.parseDouble(input);
}
input = JOptionPane.showInputDialog("What is the score " +
"of your second test?");
testScore2 = Double.parseDouble(input);
while (testScore2 < 1 || testScore2 > 100)
{
input = JOptionPane.showInputDialog("This test score is not " +
"between 1 and 100. \nPlease enter a test score in " +
"this range:");
testScore2 = Double.parseDouble(input);
}
input = JOptionPane.showInputDialog("What is the score " +
"of your third test?");
testScore3 = Double.parseDouble(input);
while (testScore3 < 1 || testScore3 > 100)
{
input = JOptionPane.showInputDialog("This test score is not " +
"between 1 and 100. \nPlease enter a test score in " +
"this range:");
testScore3 = Double.parseDouble(input);
}
// calculate average and display output
average = (testScore1 + testScore2 + testScore3)/3;
JOptionPane.showMessageDialog(null, name + ", your average score is: " + average);
}
First off, I'm a beginner programmer. My terminology and jargon are quite lacking, so bear with me.
I'm writing a program to capture 3 test scores then validate them using a while loop (must be within the 1-100 range). The test scores are then averaged and the output displays the average. Pretty simple stuff.
I'm wanting to find a way, if possible, to capture the number of test scores, then from there, capture each actual score. For example, the program asks "How many tests are being computed for average?", then take that number and have it be the same amount of times the program prompts, "Please enter test score (1):" or something along those lines. So for further clarity, if the user typed 4 for number of tests, then the prompt for inputting the score would show up 4 times.
I feel the above code is redundant by using a while loop for each score and at that, limited because the program is only meant for 3 scores. Any help is much appreciated and feel free to critique anything else in the code.

Yes you can.
What you need is a nested loop. In pseudo code:
while(condition)
{
int numberOfInput = getInput() ; //get the input from the user
for(int i =0 ; i < numberOfInput; i++) //iterate for the amount of prompts required
prompt() ; //get input
}
function prompt
while (testScore1 < 1 || testScore1 > 100)
{
input = JOptionPane.showInputDialog("This test score is not " +
"between 1 and 100. \nPlease enter a test score in " +
"this range:");
testScore1 = Double.parseDouble(input);
}

Short answer:Yes, it is possible.
Option 1: Initially ask the user how many scores they are planning on entering, and store that in an int variable.
For example:
Ask user how many scores to enter.
Check the response, and store it in an int variable.
Create a double variable to add the scores (initialize it to 0.0)
Use a for loop, asking for the score;
Evaluate the score to ensure it's a valid number
If it's not a valid number, prompt the user again (this is still within
the same iteration, not a different iteration)
If it's a valid number, add it to the total scores variable
Once loop is exhausted, just divide the two variables (since the total
scores is a double, your answer will automatically be a double)
Display the answer.
Option 2: Use a sentinel-loop (the user has to enter a letter -usually 'Q' or 'N'- or something to exit the loop)
Create an int variable to store total loops (initialize to 0).
Create a double variable to add the scores (initialize it to 0.0)
Use a for loop, asking for the score;
Check if the value is the quit character
If it is not
Evaluate the score to ensure it's a valid number
If it's not a valid number, prompt the user again (this is still within
the same iteration, not a different iteration)
If it's a valid number, add it to the total scores variable and increment
the total loops variable by 1.
If it is
just divide the two variables (since the total
scores is a double, your answer will automatically be a double)
Display the answer.
Hope it helps.

In http://korada-sanath.blogspot.in/p/discussion-on-tech-topics.html, there is a pseudo code which illustrates similar problem with basic Java programming skills. In that in looping section you can simply add a check whether user entered score is in range 1-100 or not. If not, you can decrease loop variable by '1' so that user can enter his score one more time...
For further illustration please add below code in looping section of code present in above mentioned link.
instead of directly assigning user entered value to your testScores array, you can use one temp var and then can assign if user entered score in range.
Double temp = Double.parseDouble(br.readLine());
if(temp > 1 && temp < 100) {
testScores[loopVar] = temp;
} else {
loopVar--;
}

Why is this giving me an infinite loop?

I was going through a code used to calculate investments until it has doubled and I received an infinite loop that I can't seem to solve. Can anyone figure out why this is giving me an infinite loop? I've gone through myself but I can't seem to find the problem. The "period" referred is how many times per year the interest is compounded.
double account = 0; //declares the variables to be used
double base = 0;
double interest = 0;
double rate = 0;
double result = 0;
double times = 0;
int years = 0;
int j;
System.out.println("This is a program that calculates interest.");
Scanner kbReader = new Scanner(System.in); //enters in all data
System.out.print("Enter account balance: ");
account = kbReader.nextDouble();
System.out.print("Enter interest rate (as decimal): ");
rate = kbReader.nextDouble();
System.out.println(" " + "Years to double" + " " + "Ending balance");
base = account;
result = account;
for (j=0; j<3; j++){
System.out.print("Enter period: ");
times = kbReader.nextDouble();
while (account < base*2){
interest = account * rate / times;
account = interest + base;
years++;
}
account = (((int)(account * 100))/100.0);
//results
System.out.print(" " + i + " " + account + "\n");
account = result;
}
The code should ask for three "periods", or three different times the entered data is compounded per year (ex annually, monthly, daily etc.)
Thanks a lot!

Instead of doing
account =interest +base
You should have
account = interest +account

You should add some sanity checking. Either check if all the numbers will result in a finite number of loops (account and rate != 0, maybe some other stuff), or more simply, break if you've looped more times than would be reasonable (say 1000 for instance). My guess is that rate is 0 resulting in no increase in account, therefore it will loop forever.
You have a calculation error:
account = interest + base;
Presumably this should be:
account = account + interest;
Also, are you sure you want to have the int cast?
account = (((int)(account * 100))/100.0);
You're throwing away the values smaller than 1 cent apparently. However, if the interest is too small you will not get any change.

The reason it may loop forever is that the double calculation of account is effectively truncated by casting to int, so it may never change if rate is too small and the new value of account isn't made larger by at least 0.005.