I'm trying to code shopping cart program, using Arraylist. I want to make this --> when the user types 1 or Add item(s), it adds the (quantity, name, price) of the item that user wanted to add. But, I get errors in the very last part, since the "cart" cannot be resolved. I know this is because "ArrayList cart = new ArrayList(i);" is in the for loops, but I don't know how to fix this. Also, am I using Arraylist correctly? I've been struggling for 3 days and still not sure..

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Scanner;

public class item {

    public item(int quantity, String name, double price) {
    
    }


    public static void main(String[] args) 
    {
        item();
    
    }//end main

    
    public static void item()
    {
        Scanner myinput = new Scanner(System.in);
        int total ;
        int quantity;
        String name = null;
        double price;
        String option;

        System.out.println("How many kind of items do you have?");
        total = myinput.nextInt();

        for (int i = 1; i<=total; i  )
        {
            System.out.println("Please type the quantity of your item(s) (ex : If you have 2 shirts, please type 2)");
            quantity = myinput.nextInt();
            if (quantity == 0)
            {
                break;
            }

            System.out.println("Please type the name of your item(s)");
            name = myinput.next();

            System.out.println("Please type the price of your item(s)");
            price = myinput.nextDouble();
            
            ArrayList<item> cart = new ArrayList<item>(i);
            
        }


        System.out.println("Please choose one option below \n1) Add item(s) \n2) Remove item(s) \n3) View Cart \n4) Checkout \n5) Exit");
        option = myinput.next();

        switch(option)
        {
        case "1" , "Add item(s)": 
            System.out.print("Please type the name of your item(s)");
        name = myinput.next();

        System.out.print("Please type the price of your item(s)");
        price = myinput.nextDouble();

        System.out.print("Please type the quantity of your item(s)");
        quantity = myinput.nextInt();

        cart.add(new item(quantity, name, price)); //gets error in "cart"
        System.out.println(Arrays.toString(cart)); //gets error in "cart"**strong text**
        break;
        }


    }//end item
    
}//end class

CodePudding user response：

In your switch statement, you refer to a variable called cart. But no such variable exists at that point.

The only cart you have is defined within your for loop. So each time through the loop, you instantiate a new cart (a new ArrayList object), and immediately discard it. At loop’s end, any variables defined within the loop, and never shared outside the loop, instantly become candidates for garbage-collection, become unreachable to you, and will eventually be deleted by the garbage collector.

At the point the flow-of-control reaches your switch, no cart object remains available to your code.