Deleting a selected Item using linked hash map

Question

I have a basket where products are added to and for each product there is a delete button:

Whenever I click the bottom button it deletes the bottom product, the problem is it also deletes the last item when clicked in the top button until the amount is 0 and the item is gone it deletes the 2nd one on the bottom (in this case the first item)

Here is my basket class code:

package model;

import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Observable;
import main.WinkelApplication;
import view.Payment;

public class Basket extends Observable {

    private final Map<Product, Integer> products;

    public Basket() {
        super();
        products = new LinkedHashMap<Product, Integer>(); //Map zorgt ervoor dat keys??? aan values word gebonden (dit is een soort van variabele[i], i staat voor de key
    }

    public void addProduct(Product product) {
        // check if product is allready added to the basket
        if (products.containsKey(product)) {
            products.put(product, products.get(product) + 1);

        } else {
            products.put(product, 1); 
        }
        setChanged();
        notifyObservers();
    }

    public void deleteProduct(Product product) {
        // check if product is allready added to the basket
        int i = WinkelApplication.getBasket().getProductAmount(product);
        int id = product.getProductId();


        if (WinkelApplication.getBasket().getProductAmount(product) == 1) {

            products.remove(product);
            WinkelApplication.getInstance().showPanel(new view.Payment());

        }else{
            i--;
            products.put(product, i);
            WinkelApplication.getInstance().showPanel(new view.Payment());
        }

        if (products.size() == 0) {
            WinkelApplication.getInstance().showPanel(new view.CategoryList());
        }
    }

    public void empty() {
        products.clear();
        setChanged();
        notifyObservers();
    }

    public List<Product> getProducts() {
        List<Product> list = new LinkedList<Product>(products.keySet());
        return list;
    }

    public int getProductAmount(Product product) {
        return products.get(product);
    }

    public int size() {
        return products.size();
    }

    public double getTotalCosts() {
        double total = 0.0;
        for (Entry<Product, Integer> entry : products.entrySet()) {  //gaat de lijst van producten af in basket, en doet de prijs bij totaal * het hoeveelheid van zo'n product
            total += entry.getKey().getPrice() * entry.getValue();
        }
        return total;
    }
}

As seen in the deleteProduct method I did products.remove(product) so I assume it then takes the last Item, if I System out the hash map it shows me: {Cars=2, Dames onderbroek=1} (according to the picture above). How can I make sure it deletes the selected one instead of the last one in the list?

The product class:

package model;

public class Product {

    private int productId;
    private int categorieId;
    private String name;
    private String description;
    private double price;

    public Product() {
        this(-1, -1, "", "", 0.0);
    }

    public Product(int product_id, int categorie_id, String name, String description, double price) {
        this.productId = product_id;
        this.categorieId = categorie_id;
        this.name = name;
        this.description = description;
        this.price = price;
    }

    /**
     * @return the productId
     */
    public int getProductId() {
        return productId;
    }

    /**
     * @param productId the productId to set
     */
    public void setProductId(int productId) {
        this.productId = productId;
    }

    /**
     * @return the name
     */
    public String getName() {
        return name;
    }

    /**
     * @param name the name to set
     */
    public void setName(String name) {
        this.name = name;
    }

    /**
     * @return the description
     */
    public String getDescription() {
        return description;
    }

    /**
     * @param description the description to set
     */
    public void setDescription(String description) {
        this.description = description;
    }

    /**
     * @return the price
     */
    public double getPrice() {
        return price;
    }

    /**
     * @param price the price to set
     */
    public void setPrice(double price) {
        this.price = price;
    }

    /**
     * @return the categorieId
     */
    public int getCategorieId() {
        return categorieId;
    }

    /**
     * @param categorieId the categorieId to set
     */
    public void setCategorieId(int categorieId) {
        this.categorieId = categorieId;
    }

    @Override
    public String toString() {
        return name;
    }

    @Override
    public boolean equals(Object obj) {
        boolean value;
        if (obj instanceof Product) {
            value = this.productId == ((Product)obj).productId; //VB: product1 (met ID 1) past deze methode toe, en geeft product2 als parameter: deze method geeft dan false terug.
        } else {
            value = super.equals(obj);  //van wat is Product een subclass van? en wat heeft dit voor nut?
        }
        return value;
    }

    @Override
    public int hashCode() {   //wth is dit?
        return 13 * 3 + this.productId;
    }
}

Answer 1

WinkelApplication.getBasket() maybe delivers another basket?

Not an answer but one could get an error when the product is not in products.

public int getProductAmount(Product product) {
    Integer i = products.get(product);
    return i == null ? 0 : i.intValue();
}

Answer 2

Unfortunately you have not sent us the class Product but I can assume that you have not implemented hashCode() and equals() for this class.

The short answer - do this and your logic will work.

The longer answer is that hash mechanism uses these methods to identify your object. By default hashCode() returns the "address" in java heap, so 2 different instances of Product are different even if all their fields are equal. Pay attention that if equals() returns true hashCode() must return equal value for both objects.