getting an error on java-objects/delivering-the-mvp/defaulting-parameters challenge

Right, I'm back at my computer now so I'll add a little more to that answer.

In this challenge you are creating a new method that is called the same as an existing one, addItem.

The difference is that the method you are creating has a different method signature; in this case, the number of parameters are different. The existing addItem method receives a Product and a quantity. It then adds quantity of Product into your ShoppingCart. The new method just receives a Product as it will always just add one of that Product to your cart.

The line of code that needs to work is:

cart.addItem(dispenser);

As you can see, this doesn't fit the existing addItem method, which takes two parameters:

  public void addItem(Product item, int quantity) { // two parameters
    System.out.printf("Adding %d of %s to the cart.%n", quantity, item.getName());
    /* Other code omitted for clarity. Please imagine
       lots and lots of code here. Don't repeat it. 
    */
  }

The existing addItem method has lots of code hidden - we don't want to be duplicating any of that. But we need to change something so that it takes only one parameter. The existing method remains a requirement; we can't delete it as it is needed for instance where multiple items are added to the cart.

The new method takes a single parameter, an instance of Product and results in one of that product being added to the cart. The method signature takes one parameter:

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

Inside that method, we call the existing addItem method but default the quantity to 1. That's what you've written already - it was just in the wrong place!

Now, if you've uncommented the line in Example.java your code should work. But remove your method definition from around it first.

I hope that helps.

Steve.