VERY CONFUSED WITH - fill(MAX_PEZ); and Challenge Task (GoKart)

Q1: I think you may have confused the intended use of the fill() method from the example with what is needed in the code challenge. In the example, we are filling the PezDispenser up to its maximum capacity, which is defined in the constant MAX_PEZ.

edit: I think I actually misunderstood your first question too lol. Looking back at this—was reviewing with my gf, she was having an issue with the same challenge last night—it looks like you are actually asking "Why are we defining and using a function instead of just changing the variable." This is understandable, and basically, it's just a better defined and more flexible way of doing things. You can understand the intention behind the variable name fill() and you also get the benefit of being able to call that whenever you want instead of re-typing the same code. DRY: don't repeat yourself! Imagine if you also had to increment a refill counter variable to keep track of how many times the dispenser was refilled? The more complexity and features you add, the more you will want to define your objects by their behaviors through functions.

Q2a: In the code challenge they are asking you to modify your drive method to accept an int argument for the number of laps to drive, and then to increase/decrease your member variables—lapsDriven & barCount—accordingly. The difference, and the source of your confusion, is more likely in the understanding of the problem and its translation into code. To aid your understanding of the terminology, think of parameter as meaning the things the method requires to run and arguments as the actual values/variables/objects that are passed to a method when it is called.

Q2b: This is asking to create another drive method that accepts no parameters. Essentially, you are creating what is called an "overloaded" method. You can have as many methods named drive as you might want, so long as they define different types for their parameters, or the types of their listed parameters are in a unique order.

In this case, they are basically asking for a much simpler version of your new drive method—much like you had it before, that also utilizes the newly added method for optimal maintainability. One thing to also consider is that we imposed the restriction that only one lap could be driven at a time when calling drive(). In reality, this is technically a constant, and not some arbitrary number; in my example below I've defined it as a constant that more clearly demonstrates its intention in its variable name.

example of an overloaded method:

public class Dog {
  private static final int BARK_COUNT_DEFAULT = 1;  

  public void bark() {
    bark(BARK_COUNT_DEFAULT);
  }

  public void bark(int numOfTimesToBark) {
    //your code defining WHAT SPECIFICALLY to do when barking goes here...
    //and because bark() calls this version, you only have to write that code once
  }

}

think it is:

public void drive() { drive(1); }