Extra Credit!

Method fillUp is not designed well:  When calling fillUp(int,boolean) for an IceCreamMachine object, the method in class VendingMachine is called.  This means that the variable coolingOk is not set as it would be for fillup(int).  One way to solve this problem would be to override fillUp(int,boolean) in class IceCreamMachine by supplying a method that handles the check on maxFillup properly.

As an exercise in understanding overloading, overriding, and polymorphism you can gain 10 points extra credit by implementing the methods fillUp(int) and fillUp(int,boolean) in VendingMachine, such that with one of the two methods (fillUp(int) and fillUp(int,boolean)) alone in IceCreamMachine, both the check on maxFillup and the decision depending on removeTokens are handled properly.  You have to explain your code to me in person (during office hours, labs or after a lecture) to gain the extra credit.

Note:

• You will have to change the fillUp methods in VendingMachine to achieve this: we are looking for a better design of that class.
• You still must be able to call both fillUp(int) and fillUp(int,boolean) for IceCreamMachine objects
• both methods must do the check on maxFillUp
• only one of them is implemented in IceCreamMachine
• No class except for IceCreamMachine knows about maxFillUp.