I am new to Java and I am working on a project that works with calculating prices with/without employee discounts. After reading the following code could someone explain to me how I would need to change my code in order to get the correct output? I will explain this question in more detail at the end of the post.
Parent Class (I am NOT allowed to edit this):
public class GroceryBill {
private Employee clerk;
private List<Item> receipt;
private double total;
private double internalDiscount;
public GroceryBill(Employee clerk) {
this.clerk = clerk;
receipt = new ArrayList<Item>();
total = 0.0;
internalDiscount = 0.0;
}
public void add(Item i) {
receipt.add(i);
total += i.getPrice();
internalDiscount += i.getDiscount();
}
public double getTotal() {
return Math.rint(total * 100) / 100.0;
}
public Employee getClerk() {
return clerk;
}
public void printReceipt() {
System.out.println(this);
}
private String valueToString(double value) {
value = Math.rint(value * 100) / 100.0;
String result = "" + Math.abs(value);
if(result.indexOf(".") == result.length() - 2) {
result += "0";
}
result = "$" + result;
return result;
}
public String receiptToString() {
String build = "items:\n";
for(int i = 0; i < receipt.size(); i++) {
build += " " + receipt.get(i);
if(i != receipt.size() - 1) {
build += "\n";
}
}
return build;
}
public String toString() {
return receiptToString() + "\ntotal: " + valueToString(total);
}
public String discountToString() {
return receiptToString() + "\nsub-total: " + valueToString(total) + "\ndiscount: " + valueToString(internalDiscount) + "\ntotal: " + valueToString(total - internalDiscount);
}
public static class Employee {
private String name;
public Employee(String name) {
this.name = name;
}
public String getName() {
return name;
}
}
public static class Item {
private String name;
private double price;
private double discount;
public Item(String name, double price, double discount) {
this.name = name;
this.price = price;
this.discount = discount;
}
public double getPrice() {
return price;
}
public double getDiscount() {
return discount;
}
private String valueToString(double value) {
String result = "" + Math.abs(value);
if(result.indexOf(".") == result.length() - 2) {
result += "0";
}
result = "$" + result;
return result;
}
public String toString() {
return name + " " + valueToString(price) + " (-" + valueToString(discount) + ")";
}
}
}
Here is my code:
public class DiscountBill extends GroceryBill
{
private int myDiscountCount;
private double myDiscountAmount;
private double myPrice;
public DiscountBill(Employee clerk, boolean preferred)
{
super(clerk);
String name = "";
double price = 0;
double discount = 0;
GroceryBill.Item myBill = new GroceryBill.Item(name, price, discount);
myDiscountAmount = myBill.getDiscount();
if (myDiscountAmount > 0 && preferred)
{
myDiscountCount++;
}
}
public void add(Item myBill)
{
myPrice += myBill.getPrice();
myDiscountAmount = myBill.getDiscount();
if (myDiscountAmount > 0 )
{
myDiscountCount++;
}
}
public double getTotal()
{
if (myDiscountCount > 0)
{
return myPrice - myDiscountAmount;
}
return myPrice;
}
public int getDiscountCount()
{
return myDiscountCount;
}
public double getDiscountAmount()
{
return myDiscountAmount;
}
public double getDiscountPercent()
{
return ((myPrice - myDiscountAmount) / myPrice * 100);
}
}
Lastly, here is the expected output followed by my specific question:
The outputs that I am getting for my methods are one step ahead of where they should be. That is to say, my getTotal, for example, should start out as 1.35 (the first value input by the website I am using that tests my child class that I wrote) and then after another step it should be reduced to 1.1 (the website uses the employee discount using the boolean preferred from the constructor), but my program outputs 1.1 because my child class overrides the parent class's getTotal() method and never starts at the total it should (1.35). Basically I need to know how to get those original values from my parent class and THEN use the override methods to get the values after they are changed. If you want to see how this website operates, here is a link to the question I'm working on.
P.S. Please let me know if I need to give more/less information and ways that I can clean up this post or make it easier to understand. If my question was too broad, please ask me what you don't understand about it and I'll try my best to tell you! Thank you!
I'm not sure if that is what you want. Do you want to call parent method?
For that you can use super.parentMethodName
Please correct me if I'm wrong
As far as I understood your question, what you want to do is :
Add this additional code to your DiscountBill
public class DiscountBill extends GroceryBill
{
private static boolean isFirstTime = true;
public double getTotal()
{
if (!isFirstTime && myDiscountCount > 0)
{
return myPrice - myDiscountAmount;
}
isFirstTime = false;
return myPrice;
}
}
Related
I'm looking for help on an error that I am getting while trying to create this java class. I want to add test scores as well as the average for this student class. I have tried a lot of things and I cant seem to get the error "Variable declaratorid expected after this method" to go away when I reach my setTestScore method shown below (shown with arrows) similarly in my next getTestScore method I have an error "cant invoke getTest() on the primitive type int." (also show with arrows)
public class Student {
private String firstName, lastName;
private Address homeAddress, schoolAddress;
private int TestScore, testScores ;
private int testScore1, testScore2, testScore3;;
public void TestScore(int testScore1, int testScore2, int testScore3)
{
this.testScore1 = testScore1;
this.testScore2 = testScore2;
this.testScore3 = testScore3;
}
public Student(String first, String last, Address home, Address school)
{
this.firstName = first;
this.lastName = last;
this.homeAddress = home;
this.schoolAddress = school;
}
testScores = new TestScore(testScore1, testScore2, testScore3);
public void setTestScore(int testNumber, int TestScore) {
if(testNumber==1) {
testScores.setTest1(>>testScore<<);
}
else if(testNumber==2) {
testScores.setTest2(>>testScore<<);
}
else if(testNumber==3) {
testScores.setTest3(>>testScore<<);
}
}
public void setTest1(int test1) {
this.testScore1 = test1;
}
public void setTest2(int test2) {
this.testScore2 = test2;
}
public void setTest3(int test3) {
this.testScore3 = test3;
}
public int getTestScore(int testNumber) {
if(testNumber==1) {
return >>testScores.getTest1<<();
}
else if(testNumber==2) {
return >>testScores.getTest2<<();
}
else if(testNumber==3) {
return >>testScores.getTest3<<();
}
else {
return 0;
}
}
public int getTest1() {
return testScore1;
}
public int getTest2() {
return testScore2;
}
public int getTest3() {
return testScore3;
}
public double getAverageTestScores() {
double avg;
avg=(testScores.getTest1() + testScores.getTest2() + testScores.getTest3())/3.0;
return avg;
}
public String toString()
{
String result;
result = firstName + " " + lastName + "\n";
result += "Home Address:\n" + homeAddress + "\n";
result += "School Address:\n" + schoolAddress + "\n";
result +="Test Score 1:\n" + testScores.getTest1() + "\n";
result +="Test Score 2:\n" + testScores.getTest2() + "\n";
result +="TestScore 3:\n" + testScores.getTest3() + "\n";
result +="Average test score:\n" + getAverageTestScores() + "\n";
return result;
}
}
remove this statement
testScores = new TestScore(testScore1, testScore2, testScore3);
and where ever you have used
testScores.foo
in your program,replace it with
this.foo
remove this statement
testScores = new TestScore(testScore1, testScore2, testScore3);
and where ever you have used
testScores.foo
in your program,replace it with
this.foo
Ok so basically this is my program it's about Students & Student Groups;
Each student has a name, ID and marks/points;
The program is working fine but what's missing is that the SUM function in the class StudentsGroup needs to be static and to take a parameter of the "Group" of which you need the sum of points. My problem is that when I put the function and the ArrayList to static, the function returns both of the groups score combined and I don't know how to make it work
//the program works correctly and returns the correct values about
everything; i only get those errors when i try to change the
sumOfPoints function to static
the two files that i have are:
Group 1:
61662126 Laurel 50
61662213 Mark 35.5
61662345 Yanny 67
61662127 Larry 27
61662125 Kevin 87.5
and Group 2:
61662126 Jason 70
61662213 Josh 25.5
61662345 Bobby 57
61662127 Megan 17
61662125 Drake 86.5
the correct output should be:
Total points of Group1: 267.0
Total points of Group2: 256.0
Comparing Group1 to Group2: 1
but when i put it to static it returns 523 in both which is both of the groups combined and i don't understand what im doing wrong
public interface IFile
{
public void Load();
}
public class Student implements Comparable<Student>
{
private int facnum;
private String name;
private double points;
public Student(int fn, String n, double p)
{
this.facnum = fn;
this.name = n;
this.points = p;
}
public void SetFN(int fn)
{
this.facnum = fn;
}
public void SetName(String n)
{
this.name = n;
}
public void SetPoints(double p)
{
this.points = p;
}
public int GetFN()
{
return this.facnum;
}
public String GetName()
{
return this.name;
}
public double GetPoints()
{
return this.points;
}
public boolean equals(Object s)
{
if (this.GetFN() != ((Student)s).GetFN())
{
return false;
}
return true;
}
public int compareTo(Object s)
{
if(this.GetFN() < ((Student)s).GetFN())
{
return -1;
}
if(this.GetFN() > ((Student)s).GetFN())
{
return 1;
}
return 0;
}
public String toString()
{
return "Faculty Number: " + this.facnum + " Name: " + this.name + " Points: " + this.points + " \n";
}
}
import java.io.*;
import java.util.*;
public class StudentsGroup implements IFile, Comparable<Object>
{
private String groupname;
private List<Student>oStudent = new ArrayList<Student>();
public StudentsGroup(String filename)
{
this.groupname = filename;
Load();
}
public void Load(){
try
{
Scanner sc=new Scanner(new File(this.groupname));
while(sc.hasNextLine())
{
oStudent.add(new Student(sc.nextInt(),sc.next(),
sc.nextDouble()));
}
sc.close();
}
catch(IOException e)
{
System.out.println("Input/Output Error...");
}
}
public void printColl()
{
System.out.println(oStudent.toString());
}
public List<Student> sortedListFN()
{
Collections.sort(oStudent);
return oStudent;
}
public double sumOfPoints()
{
double sum = 0.00;
for(Iterator<Student> it= oStudent.iterator(); it.hasNext();)
{
Student c = it.next();
sum += c.GetPoints();
}
return sum;
}
public int compareTo(Object s)
{
if(this.sumOfPoints() < ((StudentsGroup) s).sumOfPoints())
{
return -1;
}
if(this.sumOfPoints() > ((StudentsGroup) s).sumOfPoints())
{
return 1;
}
return 0;
}
public static void main(String[] args)
{
StudentsGroup oGroup1 = new StudentsGroup("Group1.txt");
oGroup1.printColl();
System.out.println("Sorted order by FN: " + oGroup1.sortedListFN() + "\n");
StudentsGroup oGroup2 = new StudentsGroup("Group2.txt");
System.out.println("Total points of Group1: " + oGroup1.sumOfPoints() + "\n");
System.out.println("Total points of Group2: " + oGroup2.sumOfPoints() + "\n");
System.out.println("Comparing Group1 to Group2: " + oGroup1.compareTo(oGroup2));
}
}
edit//the static method that i tried is changing oStudent to static:
private static List<Student>oStudent = new ArrayList<Student>();
obviously changing the sum function to static & editing the compareTo method:
public static double sumOfPoints(Object s)
{
double sum = 0.00;
s = new ArrayList<Student>(oStudent);
for(Iterator<Student> it= ((List<Student>) s).iterator(); it.hasNext();)
{
Student c = it.next();
sum += c.GetPoints();
}
return sum;
}
public int compareTo(Object s)
{
if(this.sumOfPoints(this) < ((StudentsGroup) s).sumOfPoints(s))
{
return -1;
}
if(this.sumOfPoints(this) > ((StudentsGroup) s).sumOfPoints(s))
{
return 1;
}
return 0;
}
and the output:
System.out.println("Total points of Group1: " + oGroup1.sumOfPoints(oGroup1) + "\n");
System.out.println("Total points of Group2: " + oGroup2.sumOfPoints(oGroup2) + "\n");
System.out.println("Comparing Group1 to Group2: " + oGroup1.compareTo(oGroup2));
and the output starts returning 523
Your static method overwrites s with the inner object of that particular instance class:
s = new ArrayList<Student>(oStudent);
I think your mistake is here. This is not how you use a static method of class. The correct way to do it is StudentsGroup.sumOfPoints(yourObjectHere). A static method should not know about any field of a particular instance.
I'm trying to figure out another way to keep track of the current weight of a suitcase, at the moment I use an instance variable but I'm only allowed to use 2 which is a list of items in the suitcase and the max weight.
What would be a way to do this? I've tried creating another method but I just can't figure out a way to do it without using an instance variable.
my code for Suitcase.java:
ArrayList<Thing> things; // List stores name of object and weight of object
private int weight; // Need to get rid of this
private int maxWeight;
public Suitcase(int weight) {
this.maxWeight = weight;
this.weight = 0; // and this?
this.things = new ArrayList<Thing>();
}
public void addThing(Thing thing) { // Need to modify this as well
if (weight < this.maxWeight) {
things.add(thing);
weight += thing.getWeight();
if (weight > this.maxWeight) {
weight -= thing.getWeight();
things.remove(things.size() - 1);
}
}
}
public Thing heaviestThing() {
if (!things.isEmpty()) {
for (int i = 0; i < things.size(); i++) {
}
}
return null;
}
public void printThings() {
for (Thing thing : things) {
System.out.println(thing);
}
}
public int totalWeight() {
return this.maxWeight;
}
#Override
public String toString() { // This is where I have problems because I need to keep track of current weight.
if (things.isEmpty()) {
return "empty (" + weight + " kg)";
} else if (things.size() == 1) {
return things.size() + " thing (" + weight + " kg)";
} else {
return things.size() + " things (" + weight + " kg)";
}
}
My code for Thing.java
private String name;
private int weight;
public Thing(String name, int weight) {
this.name = name;
this.weight = weight;
}
public String getName() {
return this.name;
}
public int getWeight() {
return this.weight;
}
#Override
public String toString() {
return this.name + " (" + weight + " kg)";
}
Instead of int maxWeight, why not create a method calculateWeight():
public int calculateWeight() {
int weight = 0;
for (Thing thing : things) {
weight += thing.getWeight();
}
return weight;
}
I want to make an array of objects and use it in different functions. I wrote this pseudocode
privat stock[] d;
privat stock example;
public void StockCheck(){
d =new stock[2];
d[0]= new stock("a","test1", 22);
d[1]= new stock("b","test2", 34);
}
#Override
public stock getStock(String name) throws StockCheckNotFoundException{
int i;
System.out.println("ok" + name + d.legth); // error
example = new stock("example","example",2);
return example;
}
In class test I make an instance of getStock and I call the function getStock stock.getStock();
I get a NullPointerExeption when I do d.length. d is null but I don't understand why.
Hmmmm. If that is in any way like your real code, then the problem is that your "constructor" isn't really a constructor, as you've declared it to return void, making it an ordinary method instead. Remove tbat "void" and it may fix the problem!
Perhaps this example of code will do what you need, using three classes
Test - the main test code
Stock - the implied code for Stock from your question
StockCheck - the corrected code from your question.
(Note: you may really want to use an ArrayList inside StockQuote so you can add and delete Stocks.)
Test class
package stackJavaExample;
public class Test {
public static void main(String[] args) {
String[] testNames = {"test1","test2","notThere"};
StockCheck mStockCheck = new StockCheck();
for (int i=0; i<testNames.length; i++) {
Stock result = mStockCheck.getStock(testNames[i]);
if (result == null) {
System.out.println("No stock for name: " + testNames[i]);
} else {
System.out.println("Found stock: " + result.getName() + ", " + result.getSymbol() + ", " + result.getValue());
}
}
}
}
Stock class
package stackJavaExample;
public class Stock {
private String symbol;
private String name;
private double value;
public Stock(String symbol, String name, double value) {
this.symbol = symbol;
this.name = name;
this.value = value;
}
public String getSymbol() { return symbol;}
public String getName() { return name;}
public double getValue() {return value;}
}
StockCheck class
package stackJavaExample;
public class StockCheck {
private Stock[] d;
public StockCheck() {
d = new Stock[2];
d[0] = new Stock("a","test1", 22);
d[1] = new Stock("b","test2", 34);
}
public Stock getStock(String name) {
for (int i=0; i < d.length; i++) {
if (d[i].getName().equalsIgnoreCase(name)) {
return d[i];
}
}
return null;
}
}
I'm not entirely sure how I would do this, here is my code:
public class PizzaMenu
{
static Map<String,Pizza> namedPizzas= new HashMap<String,Pizza>();
public static void main(String[] args)
{
}
public static void addItem(String name, Pizza pizza)
{
namedPizzas.put(name, pizza);
}
public String printMenu()
{
/*
String menuString="";
for (Every menu item)
{
//Add name of menu item to menuString with carriage return
//Add details of menu item (pizza.getInfo();) to menuString
}
*/
//return menuString
}
}
I would then call System.out.println(PizzaMenu.printMenu()) in another class. The sort of format I'm hoping to achieve is as follows:
/*
* PizzaName
* Details
*
* Next PizzaName in menu
* Details
*
* Next PizzaName in menu
* Details
*
*
*
*/
Am I maybe using the wrong data structure for this type of operation or is there a way of achieving this?
Here is the structure of the Pizza class (apologies for poor formatting):
public class Pizza
{
private double cost;
private Boolean veg;
private PizzaBase base;
private List<PizzaTopping> toppings = new ArrayList<PizzaTopping>();
public Pizza(PizzaBase base, PizzaTopping topping) //Constructor for pizza with 1 topping
{
setBase (base);
toppings.add(topping);
}
public Pizza(PizzaBase base, PizzaTopping topping, PizzaTopping topping2) //Constructor for pizza with 2 toppings
{
setBase (base);
toppings.add(topping);
toppings.add(topping2);
}
public Pizza(PizzaBase base, PizzaTopping topping, PizzaTopping topping2, PizzaTopping topping3) //Constructor for pizza with 3 toppings
{
setBase (base);
toppings.add(topping);
toppings.add(topping2);
toppings.add(topping3);
}
public double getCost()
{
return cost;
}
public void setCost(double cost)
{
this.cost = cost;
}
public PizzaBase getBase()
{
return base;
}
public void setBase(PizzaBase base)
{
this.base = base;
}
public List<PizzaTopping> getToppings()
{
return this.toppings;
}
public String getToppingsInfo()
{
String toppingInfo = "\n";
PizzaTopping t;
for (int i = 0; i<getToppings().size();i++)
{
t = toppings.get(i);
toppingInfo=toppingInfo+t.getInfo();
}
return toppingInfo;
}
public Boolean getVeg()
{
return veg;
}
public void setVeg(Boolean veg)
{
this.veg = veg;
}
public double calculateCost()
{
PizzaTopping p;
//Loop through all ingredients and add their costs to total cost
for (int i = 0; i<toppings.size();i++)
{
p = toppings.get(i);
cost+=p.getCost();
}
cost+=base.getCost(); //Add pizza base cost to total cost
return cost;
}
//Check if pizza is vegetarian depending upon its ingredients
public Boolean isVeg()
{
Boolean toppingCheck =true;
Boolean baseCheck = true;
PizzaTopping t; //Temporary value used to stored toppings being compared in for loop
//Check each topping and check if it's suitable for vegetarians
for (int i =0; i<toppings.size();i++)
{
while (toppingCheck == true)
{
t = toppings.get(i);
if (t.getVeg()==false)
{
toppingCheck = false;
}
}
}
//Check base to see if it's suitable for vegetarians
if (getBase().getVeg()==false)
{
baseCheck = false;
}
//Return value depending on if all ingredients are suitable for vegetarians
if (toppingCheck == true && baseCheck == true)
{
return true;
}
else return false;
}
public String getInfo()
{
String vegInfo;
if (this.isVeg()==true)
{
vegInfo = "Yes";
}
else vegInfo ="No";
return String.format("Toppings:%s\n"+"Base:\n%s"+"\nTotal Cost:\t£%.2f"+"\nSuitable for vegetarians: %s", getToppingsInfo(), getBase().getInfo(), calculateCost(), vegInfo);
//Return list of toppings, Total Price, vegetarian
}
}
Try this:
String menuString="";
for (Map.Entry<String, Pizza> pizzaItem : namedPizzas.entrySet()) {
menuString += pizzaItem.getKey() + "\n";
menuString += "\t" + pizzaItem.getValue().getInfo() + "\n\n";
}
public String printMenu()
{
String s ="";
for (String key: namedPizzas.keySet()){
s+= pizzaItem.getKey() + "\n";
s+= "\t" + pizzaItem.getValue().getInfo() + "\n\n";
}
return menuString
}
To address your question directly:
You need a set of keys. With a set of keys you can also get values. HashMap#keySet should work for this. You can loop through a set using a for each loop.
Then as you said, you need to build your string and return. Putting it together gives you:
public String printMenu()
{
String menuString = "";
for(String key : namedPizzas.keySet())
{
menuString += key + "\n" +
"\t" + namedPizzas.get(key).getInfo() + "\n\n";
}
return menuString;
}
I would also like to suggest a design improvement. You should be overriding the Object#toString method for things like this. The toString method will get automatically called when you try to print the object. This allows you to do: System.out.println(myPizzaMenu); instead of System.out.println(myPizzaMenu.printMenu());
The name printMenu is also misleading, so for that reason it's also bad.
Unfortunately, after switching the map to a list, it still didn't work. An hour later I found the bug causing it all! Thanks for everyone's answers, I will keep these methods in mind when I need to use maps again.
EDIT: Here is the new class structure for reference:
public class PizzaMenu
{
static List<Pizza> namedPizzas = new ArrayList<Pizza>();
public static void main(String[] args)
{
}
public static void addItem(String name, Pizza pizza)
{
pizza.setName(name.toLowerCase());
namedPizzas.add(pizza);
}
public static String printMenu()
{
String menuString="";
Pizza p;
//Collect all pizzas and add their information to string
for (int i =0; i<namedPizzas.size(); i++)
{
p = namedPizzas.get(i);
menuString+=p.getName().toUpperCase()+"\n"+p.getInfo()+"\n\n";
p.resetCost();
}
return menuString;
}
}