We Keep Coding

If each 'transaction' is an object, how do you store the total cost of all transactions made?

Foreword: sorry for all the code, I know most of it is redundant for this question.
This class takes a description (size), a cost, and a quantity as arguments and returns the number of times the object was created (transaction_number), the total quantity specified for all the objects created (total_quantity), and (is supposed to) return the total cost of all the object created.
public class SalesTransaction
{
private static int counter = 1;
public final int transaction_number;
private static int order_quantity = 0;
public final int total_quantity;
private static double temp_grand_total = 0;
public final double grand_total;
private String size;
private double cost;
private int quantity;
public SalesTransaction(String size, double cost, int quantity)
{
this.size = size;
this.cost = cost;
this.quantity = quantity;
this.transaction_number = counter++;
order_quantity += quantity;
this.total_quantity = order_quantity;
temp_grand_total += totalCostAfterTax(cost*quantity); // this is wrong!
this.grand_total = temp_grand_total;
}
public static double discountAmount(int quantity, double cost)
{
double discount_amount = 0;
if (quantity > 20)
{
discount_amount = cost * 0.10;
}
return discount_amount;
}
public static double totalCostBeforeTax(SalesTransaction temp)
{
double total_cost;
int quantity = temp.quantity;
double cost = temp.cost;
total_cost = quantity * cost;
double discount_amount = discountAmount(quantity, total_cost);
total_cost = total_cost - discount_amount;
return total_cost;
}
public static double totalCostAfterTax(double total_cost)
{
total_cost = total_cost * 1.15;
return total_cost;
}
public static void printStats(SalesTransaction temp)
{
System.out.println("Transaction Number: " + temp.transaction_number);
System.out.println("Size: " + temp.size);
System.out.println("Cost Per Table: "+ temp.cost);
System.out.println("Number of Tables: " + temp.quantity);
System.out.println("Total Tables So Far: " + temp.total_quantity);
double total_cost_before_tax = totalCostBeforeTax(temp);
double discount_amount = discountAmount(temp.quantity, total_cost_before_tax);
System.out.println("Discount: " + discount_amount);
double total_cost_after_tax = totalCostAfterTax(total_cost_before_tax);
temp.temp_grand_total = total_cost_after_tax;
System.out.println("Cost for this transaction: " + total_cost_after_tax);
System.out.println("Total cost: "+ temp.grand_total);
System.out.println();
}
}
And this is just a tester class.
public class SalesTester
{
public static void main(String[] args)
{
SalesTransaction one = new SalesTransaction("Small", 10.0, 10);
one.printStats(one);
SalesTransaction two = new SalesTransaction("Medium", 20.0, 30);
two.printStats(two);
SalesTransaction three = new SalesTransaction("Large", 30.0, 40);
three.printStats(three);
}
}
The problem is that I can't figure out how to store the grand_total. I tried doing it the same way I stored the total_quantity but I can see why that isn't working.
How can I keep track of the grand total of all the transactions (objects) so I can then print it out on the console?
I assume there's another way of expressing this in the constructor but I'm not sure how and I couldn't find any examples of this.

The simplest solution is to use a static field on your SalesTransaction class which holds the grand_total. A static variable is shared by all instances of a class.
private static double grandTotal = 0;
public SalesTransaction(double cost) {
grandTotal += cost;
}
However, this has some disadvantages in the long run. It would mean you can't have transactions as members of different grand totals. This is why it's called the singleton anti-pattern.
A much better way to solve the problem is to make an additional class such as TransactionGroup, which contains SalesTransaction objects in a List, and sums together the costs when needed.
public class TransactionGroup {
private List<SalesTransaction> transactions = new ArrayList<>();
public void addTransaction(SalesTransaction st) {
transactions.add(st);
}
public double getGrandTotal() {
double sum = 0;
for (SalesTransaction st : transactions) {
sum += st.getCost();
}
return sum;
}
}

DemoSalesPerson2.java:15: error: constructor SalesPerson in class SalesPerson cannot be applied to given types;

Whenever I compile my code, I receive the following errors:
constructor SalesPerson in class SalesPerson cannot be applied to
given types; error: constructor Player in class Player cannot be
applied to given types;
But it doesn't list any types. The code in question is
Modify the DemoSalesperson application so each Salesperson has a successive ID number from 111 through 120 and a sales value that ranges from $25,000 to $70,000, increasing by $5,000 for each successive Salesperson. Save the file as DemoSalesperson2.java.*/
SalesPerson class:
public class SalesPerson {
// Data fields for Salesperson include an integer ID number and a double annual sales amount
private int idNumber;
private double salesAmount;
//Methods include a constructor that requires values for both data fields, as well as get and set methods for each of the data fields.
public SalesPerson(int idNum, double salesAmt) {
idNumber = idNum;
salesAmount = salesAmt;
}
public int getIdNumber() {
return idNumber;
}
public void setIdNumber(int idNum) {
idNumber = idNum;
}
public double getSalesAmount() {
return salesAmount;
}
public void setSalesAmount(double salesAmt) {
salesAmount = salesAmt;
}
}
Driver:
public class DemoSalesPerson2 {
public static void main(String[] args) {
SalesPerson s1 = new SalesPerson(111, 0);
final int NUM_PERSON = 10;
SalesPerson[] num = new SalesPerson[NUM_PERSON];
for (int x = 1; x < num.length; x++) {
// NUM_PERSON
num[x] = new SalesPerson((111 + x + "|" + 25000 + 5000 * (x)));
System.out.println(x + " " + s1.getIdNumber() + " " + s1.getSalesAmount());
}
}
}

Change this: num[x] = new SalesPerson((111 + x + "|" + 25000 + 5000 * (x)));
to this: num[x] = new SalesPerson((111 + x), (25000 + 5000 * (x)));
You had it right here SalesPerson s1 = new SalesPerson(111, 0);.
Notice the difference between the two constructor calls.
As Sssss pointed out, you're handing in a String as the constructor param when your method requires two ints.
Code jotted down here, haven't tested it. Should get you pointed in the right direction however.

public class DemoSalesPerson2
{
public static void main(String[] args)
{
SalesPerson[] num = new SalesPerson[10];
final int START_NUM =111;
final double START_SALARY=25_000;
for (int x =0; x<num.length; x++) {
num[x] =new SalesPerson(START_NUM+x,START_SALARY+5000*(x));
System.out.println(num[x].getIdNumber()+" "+num[x].getSalesAmount() );
}
}}
try this!!

Main method incorrectly displays class string?

I'm writing a program that provides the final bill for a stay at a hotel with parameters for Room #, # of guests, duration of stay, and the price per person per night.
I have the math correct in my BBRoom Class however it doesn't seem to take and process the information in the class parameters?
Driver Class:
public class BedAndBreakfastDriver {
public static void main(String[] args) {
//float price, int rmNum, int numOccupants, int duration
//or
//int rmNum, int numOccupants, int duration, float price
BBRoom Smith;
Smith = new BBRoom(29.95, 16, 1, 5);
System.out.println(Smith);
}
}
BBRoom Class:
public class BBRoom {
final int MAXCAP = 4;
final int MINCAP = 1;
final int MINSTAY = 1;
int room;
int persons;
int nights;
double cost;
double surcharge;
double cleanUp;
double cottageCost;
NumberFormat fmt1 = NumberFormat.getCurrencyInstance();
BBRoom(double price, int rmNum, int numOccupants, int duration){}
BBRoom( int rmNum, int numOccupants, int duration, double price){}
private int getRoomNumber(int rmNum){
room = rmNum;
return room;
}
private int getPersons(int numOccupants){
if (numOccupants < MINCAP){
persons = MINCAP;
}if(numOccupants > MAXCAP){
persons = MAXCAP;
}else{
persons = numOccupants;
}
return persons;
}
private int getNights(int duration){
if(duration < MINSTAY){
nights = MINSTAY;
}else{
nights = duration;
}
return nights;
}
private double setCost(double price){
return price;
}
private double getCost(double price){
if (persons < 2){
cost = price*2*nights;
}else{
cost = (persons*price*nights);
}
return cost;
}
private double BBCottage(double cost){
surcharge = (12.95*nights);
cleanUp = 47.99;
cottageCost = cost+surcharge+cleanUp;
return cottageCost;
}
public String toString(){
String bill = ("Room Number"+room+" "+"Guests:"+persons+" "+"Nights:"+nights+" "+"Basic Package:"+ fmt1.format(cost)+" "+"Cottage Upgrade:"+fmt1.format(cottageCost) );
return bill;
}
}
For some reason I keep getting the output to display every variable as
"Room Number:0 Guests:0 Nights:0 Basic Package:0.00 Cottage Upgrade:0.00"
Any help would be appreciated. Thanks!
P.S. I'd also prefer to turn my BBCottage method into a subclass but I'm not quite sure how to accomplish that. If I could get some guidance on that as well it would be great!

Your constructor has an empty body
BBRoom(double price, int rmNum, int numOccupants, int duration){} // <<<<<<< nothing going on in {}
All relevant fields are initialized to their default value of 0. Implement the constructor to do what you want.

You never actually set the values inside BBRoom. Also, the methods getVariable(int something) should be split into a separate get() and set(int something) methods, because otherwise you're simultaneously getting and setting a variable.
In your toString method, you call values that would be returned from get(), but those are never set. To fix it, you need to set them inside your constructor.

Your constructers need to set initial values.
BBRoom:
public class BBRoom {
final int MAXCAP = 4;
final int MINCAP = 1;
final int MINSTAY = 1;
int room;
int persons;
int nights;
double cost;
double surcharge;
double cleanUp;
double cottageCost;
NumberFormat fmt1 = NumberFormat.getCurrencyInstance();
BBRoom(double price, int rmNum, int numOccupants, int duration){
someInstanceVariable = price;
room = rmNum;
persons = numOccupants;
..and so on..
}
BBRoom( int rmNum, int numOccupants, int duration, double price){
..do the same here..
}
private int getRoomNumber(int rmNum){
room = rmNum;
return room;
}
private int getPersons(int numOccupants){
if (numOccupants < MINCAP){
persons = MINCAP;
}if(numOccupants > MAXCAP){
persons = MAXCAP;
}else{
persons = numOccupants;
}
return persons;
}
private int getNights(int duration){
if(duration < MINSTAY){
nights = MINSTAY;
}else{
nights = duration;
}
return nights;
}
private double setCost(double price){
return price;
}
private double getCost(double price){
if (persons < 2){
cost = price*2*nights;
}else{
cost = (persons*price*nights);
}
return cost;
}
private double BBCottage(double cost){
surcharge = (12.95*nights);
cleanUp = 47.99;
cottageCost = cost+surcharge+cleanUp;
return cottageCost;
}
public String toString(){
String bill = ("Room Number"+room+" "+"Guests:"+persons+" "+"Nights:"+nights+" "+"Basic Package:"+ fmt1.format(cost)+" "+"Cottage Upgrade:"+fmt1.format(cottageCost) );
return bill;
}
}
As for separating Cottage into another class:
BBCottage:
public class BBCottage {
public BBCottage(double cost){
surcharge = (12.95*nights);
cleanUp = 47.99;
}
public double getCottage() {
cottageCost = cost+surcharge+cleanUp;
return cottageCost;
}
}
Edit: I also realized that in your main, you're doing System.out.println(Smith);. You have print the method, not Smith. So first of all, I'd change BBRoom to have getters and setters:
void setRmNum(int rm) {
room = rm;
}
int getRmNum() {
return room;
}
Then, in your main, do System.out.println(Smith.getRmNum());

Zero value printed due to logic error in int data assignment

This code produces accurate output, aside from the final column of data output.
The output is meant to show the non-decimal vote percent value of the candidates.
An error in my logic has caused the aforementioned value to print as 0.
Output appears as follows:
public class Candidate {
public String name;
public int numVotes;
public Candidate(String name, int numVotes) {
this.name = name;
this.numVotes = numVotes;
}
public String getName() {
return name;
}
public int getNumVotes() {
return numVotes;
}
public String toString() {
return getName() + " received " + getNumVotes() + " votes.";
}
}
import java.util.*;
public class TestCandidate {
public static void main(String [] args) {
ArrayList<Candidate> list = new ArrayList<Candidate>();
list.add(new Candidate("John Smith", 5000));
list.add(new Candidate("Mary Miller", 4000));
list.add(new Candidate("Michael Duffy", 6000));
list.add(new Candidate("Tim Robinson", 2500));
list.add(new Candidate("Joe Ashtony", 1800));
System.out.println("Results per candidate:");
System.out.println("______________________\n");
int total = getTotal(list);
printVotes(list);
System.out.print("\nCandidate\t\tVotes Received\t\t% of Total Votes");
printResults(list);
System.out.println("\n\nTotal number of votes in election: " + total);
}
public static void printResults(ArrayList<Candidate> list) {
String name = "";
int percent = 0;
int votes = 0;
int total = getTotal(list);
for(Candidate token : list) {
name = token.getName();
votes = token.getNumVotes();
percent = (votes / total) * 100;
System.out.printf("\n%1s\t%12d\t%17d", name, votes, percent);
}
}
public static void printVotes(ArrayList<Candidate> list) {
for(Candidate token : list) {
System.out.println(token);
}
}
public static int getTotal(ArrayList<Candidate> list) {
int total = 0;
for(Candidate token : list) {
total += token.getNumVotes();
}
return total;
}
}

You are performing integer division here.
percent = (votes / total) * 100;
votes will always be inferior or egal than total, so it's likely that votes/total will result in 0 due to integer division.
Either change percent as double and cast one of the operand of the division to double, or if you want to keep percent as an integer, multiply vote by 100 first and then divide it by total.
percent = (votes*100) / total;

Possible fix for getting NaN in java

I have a method in the Candy Class named pricePerHundredGrams and what it is supposed to do is multiply the variable price times 100.00 and divide that answer by the variable weightGrams, and finally return that result to the variable wammy. When the variable wammy is called for in the very 2nd last statement of this code, it is supposed to pass the answer to return result. And ultimately c1 and c2 should display that result as well...but I get NaN for "per hundred grams". What is wrong with my code?
public class whatever
{ public static void main (String[] args)
{
processCandies();
System.out.println("end of processing");
}
public static void processCandies()
{
Candy c1 = new Candy("Hershey", 145, 4.35, 233);
Candy c2 = new Candy("Milky Way", 390, 2.66, 126);
System.out.println(c1);
System.out.println(c2);
}
}
class Candy
{
private String name;
private int calories;
private double price;
private double weightGrams;
double wammy = pricePerHundredGrams(price, weightGrams);
/**
Constructor
#param name
#param calories
#param price
#param gram
*/
public Candy(String n, int cal, double p, double wG)
{
name = n;
calories = cal;
price = p;
weightGrams = wG;
}
public String getName()
{
return name;
}
public int getCalories()
{
return calories;
}
public double getPrice()
{
return price;
}
public double getWeightGrams()
{
return weightGrams;
}
public double pricePerHundredGrams(double price, double weightGrams)
{
return (price * 100.00) / weightGrams;
}
public String toString()
{
String result;
result = name + "\n" + calories + " calories\n" + weightGrams + " grams\n" + wammy + " per hundred grams\n";
return result;
}
}

You are initializing wammy with the result of pricePerHundredGrams, but price and weightGrams haven't been initialized yet, so they're both 0. For double arithmetic, 0 divided by 0 is NaN (it's indeterminate in math).
Initialize wammy after price and weightGrams have valid values in your constructor:
public Candy(String n, int cal, double p, double wG)
{
name = n;
calories = cal;
price = p;
weightGrams = wG;
// Initialize wammy here.
wammy = pricePerHundredGrams(price, weightGrams);
}
Additionally, since they are already instance variables, you don't need to pass price and weightGrams as parameters to pricePerHundredGrams.