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Registering object field values Java

I've recently started programming with Java and I like to know if there is a way to register(like put in array or something) certain object field values.
In this case, for example all "name" values(private final String name) of created objects.
Any help would be greatly appreciated.
public class Item {
private int amount;
private double price;
private final String name;
private final String type;
private final String madeIn;
Item(int amount, double price, String name, String type, String madeIn){
this.amount=amount;
this.madeIn=madeIn;
this.name=name;
this.type=type;
this.price=price;
}

You have many data structures in Java in the Collection family like List or Set. You also have associative (key/value) collections with Map and its sub-classes.
Trying to read between the lines in your question, you may want to have some collection of Items that you want to access through there name field.
Assuming the name is unique in an Item and you have getters for the properties:
Map<String, Item> itemsByName = new HashMap<>();
// put some items...
itemsByName.put(item1.getName(), item1);
itemsByName.put(item2.getName(), item2);
// etc...
// Looking for an item knowing its name
String key = "Foo";
Item itemFound = itemsByName.get(key);
if (itemFound==null) {
System.out.println("There is no item whose name is " + key);
}
else {
// do something with itemFound
}

There's nothing stopping you from adding some static Set member to your class that would contain all the names of the created instances.
Inside the Item constructor you can add name to this Set.
public class Item {
private int amount;
private double price;
private final String name;
private final String type;
private final String madeIn;
private static Set<String> registeredNames = new HashSet<String>();
Item(int amount, double price, String name, String type, String madeIn)
{
registeredNames.add (name); // you should consider what you want to do
// if the same name is passed to two instances
// perhaps throw an exception
this.amount=amount;
this.madeIn=madeIn;
this.name=name;
this.type=type;
this.price=price;
}
}

Just create a static List of names and keep on adding that in the constructor like:
private final static List<String> names = new LinkedList<String>();
public Item(..) {
names.add(name);
}

Creating Java Classes

I am currently working on an inventory program involving a one dimensional array, 2 classes (Store and Book), and several other things such as methods and a constructor.
The Store class which is the main class I guess you could say is supposed to include the main() method, and is supposed to read a list of purchases from a file, process each purchase with an appropriate message (ISBN number, amount, price, or problem (such as out of stock or do not have)), store an array of up to 15 books of type Book, a method to read in the inventory file, method to process a purchase, a method to print the inventory at closing along with the number of books sold and amount made at closing.
The Book class includes, book objects (each book object holds ISBN String, price double, and copies int), constructor, getters and setters, and a method to print the information.
Since the array is supposed to be created in the Store class, but be of type Book and made up of the book objects (I'm assuming?), I'm having trouble figuring out how to do this properly (assigning values to the isbn, price, copies variables, setting up the constructor correctly, etc).
Update
The main issue I'm having right now is being able to print the book object from my printInfo method. I am getting an error message at the print statement of that method stating "cannot find symbol. symbol: book". I can't really see if the program is actually working yet since that's kind of what I need to see at this point (the printed out book object) before I start adding in a few more methods to do other things that depend on this book object being correct.
Here is the code I have come up with so far:
The Store class:
import java.util.Scanner;
import java.io.*;
public class Store {
public static void main(String[] args) throws Exception {
Book[] books = readInventory();
for (Book : books) {
System.out.printf("ISBN: %s, Price: %f, Copies: %d%n",
book.getISBN(), book.getPrice(), book.getCopies());
}
}
public static Book[] readInventory() throws Exception {
Book[] books = new Book[15];
java.io.File file = new java.io.File("../instr/prog4.dat");
Scanner fin = new Scanner(file);
String isbn;
double price;
int copies;
while (fin.hasNext()) {
for(int i = 0; i < books.length; i++) {
isbn = fin.next();
price = fin.nextDouble();
copies = fin.nextInt();
Book book = new Book(isbn, price, copies);
books[i] = book;
}
}
fin.close();
return books;
}
public static void printInfo(Book[] books) {
System.out.println(book);
}
}
And here is my Books Class:
public class Book {
private String isbn;
private double price;
private int copies;
public Book(String isbnNum, double priceOfBook, int copiesInStock) {
isbn = isbnNum;
price = priceOfBook;
copies = copiesInStock;
}
public String getISBN() {
return isbn;
}
public double getPrice() {
return price;
}
public int getCopies() {
return copies;
}
public void setISBN(String isbn) {
this.isbn = isbn;
}
public void setPrice(double price) {
this.price = price;
}
public void setCopies(int copies) {
this.copies = copies;
}
#Override
public String toString() {
return String.format("ISBN: %s, Price: %f, Copies: %d%n",
this.getISBN(), this.getPrice(), this.getCopies());
}
}
This is my first time working with classes, or at least creating multiple classes in the same program, so I'm still trying to figure out how this works. I've been reading a tutorial I found online that has been somewhat helpful, but I'm having trouble applying it to this specific type of program.
Any suggestions would be greatly appreciated.

Hi glad to see you've made the effort to actually try something before jumping on here. What you have done is pretty good so far. But what you really need now is a getter and setter method in your class Book. These will allow you to return or set the value of the variable for the object.
public class Book {
private String isbn;
private double price;
private int copies;
public Book(String isbnNum, double priceOfBook, int copiesInStock) { // Constructor?
isbn = isbnNum;
price = priceOfBook;
copies = copiesInStock;
}
public String getISBN() {
return this.isbn;
}
public double getPrice() {
return this.price;
}
public int getCopies() {
return this.copies;
}
public void setISBN(String value) {
this.isbn = value;
}
public void setPrice(double value) {
this.price = value;
}
public void setCopies(int value) {
this.copies = value;
}
}
This should help you get on the right track. Depending on how you want the information to come up would depend on whether you add System.out.println("ISBN: " + this.isbn); and so on in each get function, or you could declare a separate function getInfo which simply prints each. Or if you were returning it into store you could always print it that way. One more thing to note is that you have been declaring books as Book[] books = new Book[15] as you are creating an array of Book objects and not strings. If you need any more help let me know.

1.you shouldn't use String Array.you should declare Book Array instead. then It will be easier to assign your Book object.
for example
Book[] books = new Book[15];
books[i] = new Book(isbnNum,priceOfBook,copiesInStock);
2.because variable in Book class was declare in private type. you should create get methods in your Book class to get variable in any object.
for example
public String getbnNum()
{
return isbn;
}
public double getprice(){
return price;
}
public int getcopies(){
return copies;
}

I wrote comments in the code for you. I have to assume your file-reading code is correct since I don't have the file.
import java.util.Scanner;
public class Store {
/*
* This is the main method. It is where the code that starts off the
* application should go.
*/
public static void main(String[] args) throws Exception {
// Here, we take the array returned by the method and set it to a local variable.
Book[] books = readInventory();
// This is an alternative notation than a normal for-loop.
for (Book book : books) {
System.out.printf("ISBN: %s, Price: %f, Copies: %d%n",
book.getISBN(), book.getPrice(), book.getCopies());
}
/* Alternative to above.
for (int i = 0; i < books.length; i++) {
Book book = books[i];
System.out.printf("ISBN: %s, Price: %f, Copies: %d%n",
book.getISBN(), book.getPrice(), book.getCopies());
}
*/
}
// We add the return type of Book[] so we can get a reference to our array.
public static Book[] readInventory() throws Exception {
Book[] books = new Book[15];
java.io.File file = new java.io.File("../instr/prog4.dat");
Scanner fin = new Scanner(file);
// These variables don't need to be initialized yet.
String isbn;
double price;
int copies;
while (fin.hasNext()) {
// Fill the books array with Book objects it creates from the file.
for (int i = 0; i < books.length; i++) {
isbn = fin.next();
price = fin.nextDouble();
copies = fin.nextInt();
Book book = new Book(isbn, price, copies);
books[i] = book;
}
}
fin.close();
return books;
}
}
Book class:
public class Book {
private String isbn;
/*
* Careful using double as your type for variables that hold money values.
* If you do any division, you can end up getting answers different than
* what you might expect due to the way Java handles remainders. For that,
* make price a Currency type, which you can import from Java.util
*/
private double price;
private int copies;
public Book(String isbnNum, double priceOfBook, int copiesInStock) {
isbn = isbnNum;
price = priceOfBook;
copies = copiesInStock;
}
// This is an example of a getter method, which we need since our isbn is
// declared as private. Now, other methods can still read what isbn is.
public String getISBN() {
return isbn;
}
public double getPrice() {
return price;
}
public int getCopies() {
return copies;
}
/*
* We can use the "this" keyword to refer to this instance's isbn variable,
* instead of the local variable isbn that was passed to the method.
* Therefore, in this tricky notation we are setting the object's isbn
* variable to the isbn variable passed to the method.
*/
public void setISBN(String isbn) {
this.isbn = isbn;
}
public void setPrice(Double price) {
this.price = price;
}
public void setCopies(int copies) {
this.copies = copies;
}
}
Also note that a more advanced way to print the information for each book would be to make a toString() method in the Book class which overrides the default toString method it inherits from the generic Object class. You should use a special convention called an override annotation to do this as it is considered good practice when we redefine methods from a superclass (Object is a superclass of all objects, including Book).
#Override
public String toString() {
return String.format("ISBN: %s, Price: %f, Copies: %d%n",
this.getISBN(), this.getPrice(), this.getCopies());
}
That would allow us to simply call System.out.println(book);, for example, and would also mean we wouldn't have to rewrite all of this code every place we want to print a book. This is an important principle with objects—they generally should take care of themselves.

Making a copy of a BookOrder within BookOrder

I'm trying to make a copy of a BookOrder that I've already created, however, it isn't creating properly. So far, I have this.
public class BookOrder
{
private String author;
private String title;
private int quantity;
private double costPerBook;
private String orderDate;
private double weight;
private char type; //R,O,F,U,N
public BookOrder (String author, String title)
{
}
public BookOrder(String author, String title, int quantity, double costPerBook, String orderDate, double weight, char type)
{
this.author= author;
this.title= title;
this.quantity= quantity;
this.costPerBook= costPerBook;
this.orderDate= orderDate;
this.weight= weight;
this.type=type;
}
public BookOrder(BookOrder bookOrder)
{
}
However, when I try to copy this here:
public class TestBookOrder
{
public static void main(String[] args)
{
Scanner keyboard = new Scanner(System.in);
Utility.myInfo("11/5,2013", "Project4");
Utility.pressEnterToContinue();
Utility.clearScreen();
BookOrder BookOrder1 = new BookOrder("Jonathan", "Book1", 12, 6.75, "11/5/2013", 8.75, 'r');
System.out.print(""+ BookOrder1.invoice());
BookOrder copyA = new BookOrder(BookOrder1);
BookOrder copyB= new BookOrder(BookOrder1);
copyB.adjustQuantity(-5);
System.out.print("\n"+ copyB.invoice());
System.out.print("\n"+ copyA.invoice());
}
}
it just returns the invoice for copyA and copyB as null and 0. Anyone know what code needs to be within the copy method?

To make this work, you need to change following code. This will create a new Object and will populate same with BookOrder value passed as input. Hope this answers your doubt.
public BookOrder(BookOrder bookOrder)
{
this.author= bookOrder.getAuthor();
this.title= bookOrder.getTitle();
this.quantity= bookOrder.getQuantity();
this.costPerBook= bookOrder.getCostPerBook();
this.orderDate= bookOrder.getOrderDate();
this.weight= bookOrder.getWeight();
this.type=bookOrder.getType();
}

You need to copy the values of the parameter BookOrder into your current parameters.
e.g.,
class Foo {
private int bar;
public Foo(Foo foo) {
this.bar = foo.bar;
// same for other fields if they exist.
}
}
Incidentally, you will want to fix this:
public BookOrder (String author, String title)
{
}
You're throwing out the parameters passed into this constructor, completely ignoring them.
Edit: this was already explained to you in a previous answer to a previous question on the same assignment!

That's because you need to assign all the fields from the passed object to the current object, in the copy constructor.
public BookOrder(BookOrder bookOrder) {
this.author = bookOrder.getAuthor(); // since they are private and thus you need getter to get the values
this.title = bookOrder.getTitle();
this.quantity = bookOrder.getQuantity();
this.costPerBook = bookOrder.getCostPerBook();
this.orderDate = bookOrder.getOrderDate();
this.weight = bookOrder.getWeight();
this.type =bookOrder.getType();
}

Error: the method getId() is undefined for the type List<Product>

I have a method to create a list of objects of class
public List<Product> initProducts(){
List<Product> product = new ArrayList<Product>();
Product prod = new Product(product.getId(),product.getItemName(),product.getPrice(),product.getCount());
product.add(prod);
return product;
}
My Product class is:
public class Product {
int ItemCode;
String ItemName;
double UnitPrice;
int Count;
/**
* Initialise the fields of the item.
* #param Name The name of this member of product.
* #param id The number of this member of product.
* #param Price The price of this member of product.
*/
public Product(int id, String Name, double Price, int c)
{
ItemCode=id;
ItemName=Name;
UnitPrice=Price;
Count = c;
}
public int getId()
{
return this.ItemCode;
}
public String getItemName()
{
return this.ItemName;
}
public double getPrice()
{
return this.UnitPrice;
}
public int getCount()
{
return this.Count;
}
/**
* Print details about this members of product class to the text terminal.
*/
public void print()
{
System.out.println("ID: " + ItemCode);
System.out.println("Name: " + ItemName);
System.out.println("Staff Number: " +UnitPrice);
System.out.println("Office: " + Count);
}
}
I am getting an error that the method getId() is undefined for the type List<Product>, Similarly for other methods. Please help me out with this error.
Is my statement correct??
Product prod = new Product(product.getId(),product.getItemName(), product.getPrice(),
product.getCount());
product.add(prod);

product is a reference of List
List<Product> product = new ArrayList<Product>();
which doesn't have that method

product is reference to List object.
and List/ArrayList has no methosd named getId().
You have written getId() method for Prodct class , so you can call this method using ref to Product class object.
If you want to get any product object form list use get(int index) method of ArrayList.
eg.
Product prod = product.get(0);
String id= prod.getId();

I believe, the reason you are facing this issue is more due not following the code conventions, that any other.
Whenever you make a collection of any objects, the convention is to use plurals for reference names of the collection. And singular reference name of the Object itself.
You can find more details here.
Below is the re-written code with the code conventions being followed:
Method to create a list of objects of class Product:
public List<Product> initProducts(){
List<Product> products = new ArrayList<Product>();
Product product = new Product(products.getId(), products.getItemName(), products.getPrice(), products.getCount());
products.add(prod);
}
Product Class:
class Product {
int itemCode;
String itemName;
double unitPrice;
int count;
public Product(int itemCode, String itemName, double unitPrice, int count)
{
this.itemCode = itemCode;
this.itemName = itemName;
this.unitPrice = unitPrice;
this.count = count;
}
public int getId()
{
return this.itemCode;
}
public String getItemName()
{
return this.itemName;
}
public double getPrice()
{
return this.unitPrice;
}
public int getCount()
{
return this.count;
}
}
Now, it is easy to see, that the products Object (which is of the type List) will not have any methods name getId() or getCount(). Infact , these are methods of the Object contained in the List.
Following conventions will help you avoid, such hassles in futures.

Is my statement correct??
Product prod = new Product(product.getId(),product.getItemName(), product.getPrice(),
product.getCount());
product.add(prod);
NO this is incorrect. product is not an instance of class Product,rather it is an instance of List. List does not have any method called getId.
If you want to retrieve the elements from the list and use it to create another instance of you can do something like:
Product exisProd = product.get(0);
Product prod = new Product(exisProd .getId(),exisProd .getItemName(), exisProd .getPrice(),
exisProd .getCount());
But make sure that you have elements in the list, otherwise u may run into exception.
product.add(prod);

Java Code for Inventory Program Part 3 will not compile

Made correction to previous errors, this error now comes up.
C:\Documents and Settings\AdminUser\My Documents\InventoryPart3.java:93: invalid method declaration; return type required
public Television(int ItemNumber, String ProductName, int UnitsStock, double UnitPrice, String mfgName) {
^
1 error
Tool completed with exit code 1
class Television { //class name and attributes
private String ItemNumber; //item # of product
private String ProductName; //product name
private double UnitsStock; //# of units in stock
private double UnitPrice; //Price per unit
private String SerialNumber; //serial number of product
private double InventoryValue; //The dollar value of the inventory in stock
//constructor
public Television (String item, String product, double units, double price, String serial) {
ItemNumber = item;
ProductName = product;
UnitsStock = units;
UnitPrice = price;
SerialNumber = serial;
} //end constructor
///getter and setter methods for Television
public void setItemNumber (String item) { //setter for item number
this.ItemNumber = item;
} //end setter item number
public String getItemNumber() { //getter for item number
return ItemNumber;
} //end getter item number
public void setProductName (String product) { //setter for product name
this.ProductName = product;
} //end setter product name
public String getProductName() { //getter for product name
return ProductName;
} //end getter product name
public void setUnitsStock (double units) { //setter for units in stock
this.UnitsStock = units;
} //end setter units in stock
public double getUnitsStock() { //getter for units in stock
return UnitsStock;
} //end getter units in stock
public void setUnitPrice (double price) { //setter for unit price
this.UnitPrice = price;
} //end setter unit price
public double getUnitPrice() { //getter for unit price
return UnitPrice;
} //end getter for unit price
public void setSerialNumber (String serial) { //setter for serial number
this.SerialNumber = serial;
}//end setter for serial number
public String getSerialNumber() { //getter for serial number
return SerialNumber;
}//end getter for serial number
//calculate individual product inventory value
public double getInventoryValue(){
return UnitsStock * UnitPrice;
}//end calculate individual product inventory value
//calculate total inventory value
public double calculateInventory(){
return UnitPrice * UnitsStock;
}//end calculate total inventory value
///end getter and setter methods for Laptop
} //end class Television
class Manufacturer extends Television {
private String manufacturerName;
//constructor
public Television(int ItemNumber, String ProductName, int UnitsStock, double UnitPrice, String mfgName) {
super(ItemNumber, ProductName, UnitsStock, UnitPrice, ManufacturerName);
this.manufacturerName = mfgName;
}//end constructor
//getter and setter for class Manufacturer
public void setmanufacturerName(String mfgName) {
this.manufacturerName = mfgName;
}
public String getmanufacturerName() {
return manufacturerName;
}
//end getter and setter for class Manufacturer
//calculate total inventory value
public double calculateInventory(){
return ((UnitPrice * UnitsStock));
}//end calculate total inventory value
//calculate restocking fee method
public double getcalculateRestockFee() {
return getInventoryValue();
}//end calculate restocking fee method
}//end class Manufacturer

So there are two errors. The first one occurs on line 93 of the file InventoryPart3.java. On that line you will find the code:
super(ItemNumber, ProductName, UnitsStock, UnitPrice);
Which is actually a call to the constructor of the television class. However, the constructor of the television class accepts 5 parameters: String, String, double, double, String but you are passing only 4.
The second error occurs on line 120 of the same file. In this case you seem to be calling a method but you left out the parenthesis. That is, the code should be:
getInventoryValue()

The constructor of television which you are trying to call from the manufacturer class using super does not exist in television class. Please see the parameters in the super() call and the actual parameters in the Television constructor. The getInventoryValue function is not there in the Television class.Hence it is throwing an error for the super.getInventory call

The first error is related to your Television constructor. Your Television constructor takes 5 arguments of type String, String, double, double, String. In your Manufacturer class, you're calling the superclass constructor with an int, string, int, and double. In a subclass, your super() constructor call must match one of the constructors in the base class (Television).
For the second error, your call to getInventoryValue has a syntax error. To call a method in Java, you have to put parentheses after the name of the method:
return super.getInventoryValue() * 0.10;
Note that in this case, the super. part is optional. The getInventoryMethod() exists in the super class, and is not private, so you can call it from the subclass like this:
return getInventoryValue() * 0.10;