Project help, kinda lost

[OpX316]

I am fairly new to Java and have been working on a cash register project for a computer science class I am in. I am new to Java and a little lost here. We have 3 separate classes: Item, Transaction and Cashregister. Item and transaction were easy. You have names, item IDs, price, tax for the item class and the transaction class is basically a few ArrayLists that take all those things from the Item class and make them a transaction. What is stumping me is how I would code the Cashregister class and how I would test it in a main method. Could someone help me out a little or give some example code for a main method? That would be great. I am not asking you to do my stuff for me, but I am honestly stumped . I'll post my progress so far along with my instructions given to me by my instructor. FYI, I was given some example code to go off of for the item and transaction classes.

All 3 classes in zip form(or look below): attachments.zip - FileSmelt File and Image Hosting

Instructions:

You will not be writing a user interface for the Cash Register project. (Unless you write one to test your class.) What you are doing is writing a class which could serve as the underlying code that makes a cash register work. Your CashRegister class must have the following methods:
 
• public double getStartingCash() - returns the amount of cash in the register when it was instantiated
• public double getCurrentCash() - returns the amount of cash currently in the register
• public double getTotalChangeDispensed() - returns the total amount of change dispensed from this register
• public ArrayList<Transaction> getAllTransactions() - returns an ArrayList<Transaction> of all of the Transactions for this register
• public double getTotalChecks() - gets the total value of all checks in the register
• public int getNumberOfChecks() - gets the total number of check transactions in the register
• public double getTotalCreditTransactions() - gets the total value of all credit card transactions in the register
• public int getNumberOfCreditTransactions() - gets the total number of credit card transactions in the register
• public double getTotalDebitTransactions() - gets the total value of all credit card transactions in the register
• public int getNumberOfDebitTransactions() - gets the total number of credit card transactions in the register
• public double getTotalCashTransactions() - gets the total value of all cash transactions in the register
• public int getNumberOfCashTransactions() - gets the total number of cash transactions in the register
• public void processTransaction(Transaction t) - adds the Transaction t to the register and updates any instance variables as required
• public String receipt(int id) - returns a String with a receipt for the Transaction with the given id number, returns null if no such transaction is in the cash register
• public Transaction voidTransaction(int id) - returns the Transaction with the given ID number and voids it from the register - voiding means the transaction is removed from the collection of transactions and any instance variables which need to be updated as a result are updated (for instance the amount of cash in the register may change)

Item class:

 
 
// Note, if you are using the default package you will have to
// eliminate this line about the package.
package cashregister;
 
public class Item 
{
	private String name;
	private String idCode;
	private double price;
	private double taxRate;
 
	/**
	 * Constructs a new Item
	 * @param nm name of Item
	 * @param id id code of Item
	 * @param pr price of Item
	 * @param tr tax rate of Item
	 */
	public Item(String nm, String id, double pr, double tr)
	{
		name = nm;
		idCode = id;
		price = pr;
		taxRate = tr;
	}
 
	/**
	 * Returns the name of the Item
	 * @return name
	 */
	public String getName()
	{
		return name;
	}
 
	/**
	 * Returns the ID code of the Item
	 * @return ID code
	 */
	public String getID()
	{
		return idCode;
	}
 
	/**
	 * Returns the price of the Item
	 * @return price
	 */
	public double getPrice()
	{
		return price;
	}
 
	/**
	 * Returns the tax rate for this Item (as a decimal number,
	 * for example 6.5% = .065)
	 * @return tax rate 
	 */
	public double getTaxRate()
	{
		return taxRate;
	}
 
	/**
	 * Returns the amount of tax paid for the Item
	 * @return tax paid
	 */
	public double getTax()
	{
		return price*taxRate;
	}
 
	/**
	 * Returns the total cost (price + tax) of the Item
	 * @return total cost
	 */
	public double getCost()
	{
		return price + price*taxRate;
	}
 
	/**
	 * Sets the price of the Item
	 * @param pr new price
	 */
	public void setPrice(double pr)
	{
		price = pr;
	}
 
	/**
	 * Sets the tax rate of the Item (as a decimal number,
	 * for example 6.5% should be .065)
	 * @param tx new tax rate
	 */
	public void setTax(double tx)
	{
		taxRate = tx;
	}
 
	// Verifies the the methods work
	public static void main(String[] args)
	{
		Item it = new Item("SoBe","PN123456",1.59,.065);
		System.out.println("Name = " + it.getName());
		System.out.println("ID = " + it.getID());
		System.out.printf("Price = $%.2f\n",it.getPrice());
		System.out.printf("Tax = $%.2f\n",it.getTax());
		System.out.printf("Cost = $%.2f\n",it.getCost());
		System.out.printf("Tax Rate = %.3f\n",it.getTaxRate());
 
		it.setPrice(1.89);
		it.setTax(0.09);
		System.out.printf("New Values:\nPrice = $%.2f\n",it.getPrice());
		System.out.printf("Tax = $%.2f\n",it.getTax());
		System.out.printf("Cost = $%.2f\n",it.getCost());
		System.out.printf("Tax Rate = %.3f\n",it.getTaxRate());
	}
}

Transaction class:

package cashregister;
import java.util.ArrayList;
 
public class Transaction 
{
	private ArrayList<Item> items;
	private double totalIn;
	private String type;
	private int idNumber;
 
	private static int IDPOOL = 100000000;
 
	/**
	 * Constructor takes the amount paid in and the payment type, initializes
	 * an empty list of items.
	 * @param tp type of the payment (credit, cash, debit, check)
	 * @param in amount of payment
	 */
	public Transaction(String tp, double in)
	{
		totalIn = in;
		type = tp;
		idNumber = IDPOOL;
		IDPOOL += 1;
		items = new ArrayList<Item>();
	}
 
	/**
	 * Constructor takes the amount paid in and the payment type, as well
	 * as the ArrayList of items
	 * @param tp type of the payment (credit, cash, debit, check)
	 * @param in amount of payment
	 * @param list ArrayList of Items purchased
	 */
	public Transaction(ArrayList<Item> list, String tp, double in)
	{
		totalIn = in;
		type = tp;
		idNumber = IDPOOL;
		IDPOOL += 1;
		items = list;
	}
 
	/**
	 * Returns an ArrayList of all items in the transaction
	 * @return ArrayList<Item> of all Items in transaction
	 */
	public ArrayList<Item> getItems()
	{
		return items;
	}
 
	/**
	 * Returns the payment in for this transaction
	 * @return payment in
	 */
	public double paymentIn()
	{
		return totalIn;
	}
 
	/**
	 * Returns the change returned in this transaction
	 * @return change returned
	 */
	public double changeOut()
	{
		double temp = totalIn;
		temp -= getTaxPaid();
		temp -= subTotal();
		return temp;
	}
 
	/**
	 * Returns the subtotal for the transaction (the total of all
	 * the prices, without taxes)
	 * @return subtotal of transaction
	 */
	public double subTotal()
	{
		double sum = 0;
		for(Item temp : items)
		{
			sum += temp.getPrice();
		}
		return sum;
	}
 
	/**
	 * Returns the total taxes paid for this transaction
	 * @return taxes paid
	 */
	public double getTaxPaid()
	{
		double sum = 0;
		for(Item temp : items)
		{
			sum += temp.getPrice()*temp.getTaxRate();
		}
		return sum;
	}
 
	/**
	 * Returns the payment type (cash, credit, debit or check)
	 * @return payment type
	 */
	public String getPaymentType()
	{
		return type;
	}
 
	/**
	 * Returns the number of Items in the transaction
	 * @return number of items in transaction
	 */
	public int getTotalNumberOfItems()
	{
		return items.size();
	}
 
	/**
	 * Returns the ID number of the transaction
	 * @return ID number
	 */
	public int getID()
	{
		return idNumber;
	}
 
	/**
	 * Adds an Item to the transaction
	 * @param it Item to be added to transaction
	 */
	public void addItem(Item it)
	{
		items.add(it);
	}
 
	/**
	 * Removes an Item from the transaction, and returns it (returns null
	 * if the Item is not in the Transaction)
	 * @param it Item to be removed
	 * @return the Item removed, or null if the Item is not in transaction
	 */
	public Item voidItem(Item it)
	{
		for(Item temp : items)
		{
			if(temp.getID().compareTo(it.getID())==0)
			{
				items.remove(temp);
				return temp;
			}
		}
		return null;
	}
 
	/**
	 * Sets the payment amount and type
	 * @param in payment in
	 * @param tp type of payment
	 */
	public void setPaymentIn(double in, String tp)
	{
		totalIn = in;
		type = tp;
	}
 
 
 
	public static void main(String[] args)
	{
		Item it1 = new Item("SoBe","PN123456",1.59,.065);
		Item it2 = new Item("Twinkie","AR23471",0.99,.065);
		Item it3 = new Item("Apples","PROD33456",3.57, 0.00);
 
		Transaction trans = new Transaction("Cash",10.00);
		trans.addItem(it1);
		trans.addItem(it2);
		trans.addItem(it3);
 
		System.out.printf("\nPayment In = $%.2f",trans.paymentIn());
		System.out.printf("\nTaxes Paid = $%.2f",trans.getTaxPaid());
		System.out.printf("\nSubtotal = $%.2f",trans.subTotal());
		System.out.printf("\nTotal = $%.2f",trans.subTotal()+trans.getTaxPaid());
		System.out.printf("\nChange Out = $%.2f",trans.changeOut());
		System.out.printf("\nPayment Type:  %s",trans.getPaymentType());
		System.out.printf("\nTransaction Number:  %s",trans.getID());
		System.out.printf("\nNumber of Items = %i",trans.getTotalNumberOfItems());
 
 
		ArrayList<Item> list = new ArrayList<Item>();
		list.add(it1);
		list.add(it2);
		list.add(it3);
		trans = new Transaction(list, "credit", 6.32);
		System.out.println("\nNew Transaction:");
		System.out.printf("\nPayment In = $%.2f",trans.paymentIn());
		System.out.printf("\nTaxes Paid = $%.2f",trans.getTaxPaid());
		System.out.printf("\nSubtotal = $%.2f",trans.subTotal());
		System.out.printf("\nTotal = $%.2f",trans.subTotal()+trans.getTaxPaid());
		System.out.printf("\nChange Out = $%.2f",trans.changeOut());
		System.out.printf("\nPayment Type:  %s",trans.getPaymentType());
		System.out.printf("\nTransaction Number:  %s",trans.getID());
		System.out.printf("\nNumber of Items = %i",trans.getTotalNumberOfItems());
 
 
		trans.voidItem(it2);
		System.out.println("\nNew Transaction:");
		System.out.printf("\nPayment In = $%.2f",trans.paymentIn());
		System.out.printf("\nTaxes Paid = $%.2f",trans.getTaxPaid());
		System.out.printf("\nSubtotal = $%.2f",trans.subTotal());
		System.out.printf("\nTotal = $%.2f",trans.subTotal()+trans.getTaxPaid());
		System.out.printf("\nChange Out = $%.2f",trans.changeOut());
		System.out.printf("\nPayment Type:  %s",trans.getPaymentType());
		System.out.printf("\nTransaction Number:  %s",trans.getID());
		System.out.printf("\nNumber of Items = %i",trans.getTotalNumberOfItems());
	}
}

Incomplete CashRegister class:

package cashregister;
 
import java.util.ArrayList;
 
public class Cashregister {
	private double startinCash;
	private double currentcash;
	private double totalchange;
	private ArrayList<Transaction> transList;
 
	public Cashregister(double startCash, double curCash, ArrayList<Transaction> tran)
	{
		startinCash = startCash;
		currentcash = curCash;
		transList = tran;
	}
	public double getStartingCash()
	{
		return startinCash;
	}
	public double getCurrentCash()
	{
		return currentcash;
	}
	public double getTotalChangeDispensed()
	{
		return totalchange;
	}
	public static void main(String[] args)
	{
		Cashregister cr1 = new Cashregister(25, 23.4, transList);
 
		System.out.println(cr1);
	}
 
 
 
}

[Squiffy]

Just google "java main" -- you'll find an example of a main method straight away!

For example, if I've got a class called "Car" with a method called start() that I want to test, I could save the following in Application.java and run it:

public class Application {

public static void main(String[] args) {
Car car = new Car();
car.start();
}

}