Variable declaration and initialization in Java

Question

Where should I place this command in my code?

Item item = new Item();

I should put this inside my loop do-while so that it keeps on creating a new Item class depends on the user if how many times they want to input another product.

The problem is whenever i put that command inside my do-while , it cannot find the symbol item based on the codes at the bottom of my program. So where i should put it?

My code:

public static void main(String[] args) {

    Scanner scan = new Scanner(System. in );
    String prompt, id;
    int z = 0, choice, x = 999;
    int iprice;
    String icode;
    String iname;

    class Item {
        public int price;
        public String code;
        public String name;
    }

    ArrayList<Item> cart = new ArrayList<Item>(0);

    do {
        System.out.print("\nItem Code: ");
        icode = scan.next();
        System.out.print("Item Name: ");
        iname = scan.next();
        System.out.print("Item Price: ");
        iprice = scan.nextInt();

        item.code = icode;
        item.name = iname;
        item.price = iprice;

        cart.add(item);

        System.out.print("\tInput another? Y/N? ");
        prompt = scan.next();

    } while (prompt.equals("y"));

    System.out.println("\nWhat do you want to do?");
    System.out.println("\n1. Purchase Item ");
    System.out.println("2. List of Products ");
    System.out.println("3. Exit Program ");

    System.out.print("\n\tChoice: ");
    choice = scan.nextInt();
    if (choice == 1) {
        System.out.println("\nItem Code: ");
        id = scan.next();
        if (item.code.equals(id)) {
            System.out.println("Item Name: " + item.name);
            System.out.println("Item Price: " + item.price);
        }
    }
}

Answer 1

You should probably declare the variable outside the loop with:

Item item;

And then you should initialize it at the very beginning of the loop:

item = new Item();

This way the variable is visible troughout the class, so you won´t get the error you metioned...

Also, this basically means that you are creating a new object in each loop iteration, and you are assigning this new object to the variable item you previously declared, so your user can create as many different items as he wants...

Note that, although you are overriding the variable item in each iteration, you won´t lose the object previously attached to the variable item , because you are adding a reference to that object into your ArrayList<Item> cart when you do cart.add(item) ...

You may want to read this article about declaration of classes and objects in Java, scopes and so on...

Answer 2

It depends. You can place it outside the loop or in the class definition so that you can reuse the variable time and again and avoid having to create a local variable for each pass.
Something akin to:

Item myItem;

do{
    myItem = new Item();
    // add perfumes and shoes
    // maybe GTA 5
}while(condition)  

You need to study, what is called, variable scope . That is, where you can and cannot access a variable. Here: http://docs.oracle.com/javase/tutorial/java/javaOO/variables.html

Answer 3

create new Object inside do-while loop Item item = new Item(); i have made changes below...

public static void main(String[] args) {
            // TODO, add your application code
            Scanner scan = new Scanner (System.in);
            String prompt, id; 
            int z=0, choice, x=999;
            int iprice;
            String icode;
            String iname;


            class Item {
                public int price;
                public String code;
                public String name;

            }   

            ArrayList<Item> cart = new ArrayList<Item>(0);
             Item item; // type this
                do {

            System.out.print("\nItem Code: ");
            icode=scan.next();
            System.out.print("Item Name: ");
            iname=scan.next();
            System.out.print("Item Price: ");
            iprice=scan.nextInt();


            item = new Item();  //also create new Item(); here
            item.code=icode;
            item.name=iname;
            item.price=iprice;

            cart.add(item);

            System.out.print("\tInput another? Y/N? ");
            prompt=scan.next();
            }while (prompt.equals("y"));

            System.out.println("\nWhat do you want to do?");
            System.out.println("\n1. Purchase Item ");
            System.out.println("2. List of Products ");
            System.out.println("3. Exit Program ");
            System.out.print("\n\tChoice: ");
            choice=scan.nextInt();
             if (choice==1) {

            System.out.println("\nItem Code: ");
            id=scan.next();
                    if (item.code.equals(id)) {         
            System.out.println("Item Name: "+item.name);
            System.out.println("Item Price: "+item.price);

                    }       
             }






        }
        }