Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Java Java Objects (Retired) Delivering the MVP Defaulting Parameters

I am having trouble combining two method signature lines that take different inputs

So far I have a "bad" solution to the code challenge.

public class ShoppingCart {

public void addItem(Product item, int quantity) { System.out.printf("Adding %d of %s to the cart.%n", quantity, item.getName()); } public void addItem(Product item) { System.out.printf("Adding 1 of %s to the cart.%n", item.getName()); } }

But now I am trying to combine the two method signature lines and I am struggling to understand how it is possible to have a signature line that can take a different amount of inputs.

public class Example {

  public static void main(String[] args) {
    ShoppingCart cart = new ShoppingCart();
    Product pez = new Product("Cherry PEZ refill (12 pieces)");
    cart.addItem(pez, 5);
    /* Since a quantity of 1 is such a common argument when adding a product to the cart,
     * your fellow developers have asked you to make the following code work, as well as keeping
     * the ability to add a product and a quantity.
    Product dispenser = new Product("Yoda PEZ dispenser");
    /* Uncomment the line following this comment,
       after adding a new method using method signatures,
       to solve their request in ShoppingCart.java

public class ShoppingCart {

  public void addItem(Product item) {
  addItem(item, 1);

    System.out.printf("Adding %d of %s to the cart.%n", quantity, item.getName());
public class Product {
  /* Other code omitted for clarity, but you could imagine
     it would store price, options like size and color
  private String mName;

  public Product(String name) {
      mName = name;

  public String getName() {
      return mName;

3 Answers

Kourosh Raeen
Kourosh Raeen
23,733 Points

Hi David - You need two completely separate method definitions. The methods will have the same name but the signatures will be different. One method accepting a Product and a quantity and the other just a Product. So keep the one that's already there with two arguments and create the other one.

For your second method signature just add these lines:

 public void addItem(Product item){
   addItem(item, 1); 

In a way you are using the DRY method by using the existing method within your other method signature.