How do I avoid these messages from showing the first time user gives input

Question

So I'm making this Java application that saves products in a warehouse system and lets the customer purchase the available items, and I'm pretty much done, but this one little error in output I've been getting since the start keeps bugging me. When the program asks at first how many products the customer would like to purchase, it shows pretty much ALL the messages included in the while loop below. I know this is probably a very simple mistake to fix but I cant seem to find a proper way to fix it. This is the class:

package com.forward.forward;

import java.io.IOException;
import java.lang.reflect.Array;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.*;

public class ForwardApplication {

public static void main(String[] args)
{

    Product product1 = new Product("Fender Jazz Bass", "Bass", "Relative", "None", 400, 2016);
    Product product2 = new Product("Fender Jaguar", "Guitar", "Relative", "None", 300, 2020);
    Product product3 = new Product("Fender Mustang", "Guitar", "Relative", "None", 200, 2018);
    Product product4 = new Product("Jackson Rhodes V", "Guitar", "Relative", "None", 1000, 1998);
    Product product5 = new Product("Vox VT20+", "Amplifiers", "Relative", "None", 250, 2015);

    ProductQuantity product1Quantity = new ProductQuantity(product1, 2);
    ProductQuantity product2Quantity = new ProductQuantity(product2, 4);
    ProductQuantity product3Quantity = new ProductQuantity(product3, 3);
    ProductQuantity product4Quantity = new ProductQuantity(product4, 0);
    ProductQuantity product5Quantity = new ProductQuantity(product5, 10);

    Warehouse stock = new Warehouse();
    stock.addProductQuantity("Fender Jazz Bass", product1Quantity);
    stock.addProductQuantity("Fender Jaguar", product2Quantity);
    stock.addProductQuantity("Fender Mustang", product3Quantity);
    stock.addProductQuantity("Jackson Rhodes V", product4Quantity);
    stock.addProductQuantity("Vox VT20+", product5Quantity);

    Scanner in = new Scanner(System.in);

    ArrayList<String> productsList = new ArrayList<>();     //list of customer products for 
ease of alphabetical re-arrangement and element wandering through cycles

    //printing available products and quantities to avoid throwing IllegalArgumentException 
from ProductQuantity
    System.out.println("Available Products:");
    System.out.println("1." + stock.storageMap.get("Fender Jazz 
Bass").getProduct().getDescription()
            + " - " + stock.storageMap.get("Fender Jazz Bass").getQuantity() + " units 
available");
    System.out.println("2." + stock.storageMap.get("Fender 
Jaguar").getProduct().getDescription()
            + " - " + stock.storageMap.get("Fender Jaguar").getQuantity() + " units 
available");
    System.out.println("3." + stock.storageMap.get("Fender 
Mustang").getProduct().getDescription()
            + " - " + stock.storageMap.get("Fender Mustang").getQuantity() + " units 
available");
    System.out.println("4." + stock.storageMap.get("Jackson Rhodes 
V").getProduct().getDescription()
            + " - " + stock.storageMap.get("Jackson Rhodes V").getQuantity() + " units 
available");
    System.out.println("5." + stock.storageMap.get("Vox VT20+").getProduct().getDescription()
            + " - " + stock.storageMap.get("Vox VT20+").getQuantity() + " units available"
    + "\n ------------------------------------------");

    System.out.println("How many products would you like to purchase?");
    int numberOfProducts = in.nextInt();

    int i = 0;
    int customerQuantity = 0;   //product quantity ordered - info received from user
    Vector<Integer> quantitiesSaver = new Vector<>();   //quantities are saved in a vector, so 
that alphabetical re-arrangement of productsList doesn't scramble the order info
    String customerNeed = ""; //customer's ordered product saved in customerNeed, to be used 
as key to access storageMap HashMap
    while (i < numberOfProducts)       //loop to show messages and receive info based on 
quantity provided in first message
    {   //MISTAKE OF OUTPUT HERE!
        System.out.println("Add product to your list (" + (numberOfProducts - i) + " left):");
        customerNeed = in.nextLine();
        if (stock.getProductQuantity(customerNeed) == 0)
        {
            System.out.println("Product no longer in stock!");
            continue;
        }
        System.out.println("Available! Product added to list.");
        productsList.add(customerNeed);
        Collections.sort(productsList, String.CASE_INSENSITIVE_ORDER);  //productsList ordered 
alphabetically
        i++;
    }

    for(i = 0; i < productsList.size(); i++)    //product quantities asked for AFTER 
alphabetical rearrangement, so quantities belong to appropriate products
    {
        System.out.println("Please provide quantity of purchase for " + productsList.get(i) + 
":");
        customerQuantity = in.nextInt();
        





  stock.storageMap.get(productsList.get(i)).setQuantity(stock.storageMap.get(productsList.get(i)).ge 
   tQuantity()
                - customerQuantity); //for more detailed info display on order.txt
        quantitiesSaver.add(customerQuantity);  //quantities now ordered in same way as the products list
    }


    List<ProductQuantity> productsOrdered = new ArrayList<>();  //list type to correspond with 
Order class structure
    for (i = 0; i < productsList.size(); i++)
    {
        productsOrdered.add(stock.storageMap.get(productsList.get(i)));
    }

    Order order = new Order();
    String output = "---Your Order---"; //output to send on order.txt

    //creating order object
    order.setListOfQuantity(productsOrdered);
    order.setId((int)(Math.random() * 1000 + 1));
    order.setDescription( "" + productsList);
    Date today = new Date();
    order.setDate(today);

    //first giving individual products ordered and other info
    for(i = 0; i < order.getListOfQuantity().size(); i++)
    {
        output = output + "\n -" + 
order.getListOfQuantity().get(i).getProduct().getDescription() +
                "\n Left in stock: " + order.getListOfQuantity().get(i).getQuantity() +
                "\n Unit price: $" + productsOrdered.get(i).getProduct().getPrice() +
                "\n Units purchased: " + quantitiesSaver.get(i) +
                ".";
    }

    //adding final order info
    output = output + "\n---Order Details---" +
            "\n Order ID: " + order.getId() +
            "\n Order Description: " + order.getDescription() +
            "\n Order Date: " + order.getDate() +
            "\n Total Cost: " + order.getTotalCost(quantitiesSaver);

    //send application output to order.txt file
    try {
        Files.writeString(Path.of("order.txt"), output);

    } catch (IOException ex) {
        ex.printStackTrace();
    }

    //system.out used for testing
    //System.out.println(quantitiesSaver);
}}

And these are the messages I get when I first provide the number of products:

How many products would you like to purchase?
1 //quantity provided by user
Add product to your list (1 left): //useless message
Product is not present in warehouse! //useless message
Product no longer in stock! //useless message
Add product to your list (1 left): //program continues normally

The ones labeled as "useless message" appear and don't do anything. Those are the ones I'm trying to get rid of.

Does this answer your question? [Scanner is skipping nextLine() after using next() or nextFoo()?](https://stackoverflow.com/questions/13102045/scanner-is-skipping-nextline-after-using-next-or-nextfoo) — Progman, Jul 23 '21 at 19:40

score -1 · Accepted Answer · answered Jul 23 '21 at 20:26

Try to add "in.nextLine();" right after " int numberOfProducts = in.nextInt(); ". I think the problem is the program read an empty line before/after it read to the input value, that is why it goes directly to your "testing" while loop and display these messages

How do I avoid these messages from showing the first time user gives input

1 Answers1