Description

Project

Turn in your work under the Google Drive folder and Google Classroom according to general guidelines.

001-CashRegister (Total 100 pts.)

Implement a CashRegister class that models a self-service cash register in the US. Imagine the customer scans the price tags of various items, sees the total purchase amount, and deposits the at least the required amount of money in the machine. The machine then dispenses the change.

step 1 (0 pts.)

Find out which methods you are asked to supply.

In a simulation, you do not have to provide every feature that occurs in the real world—there are too many. Thus, you must first clarify what the project will entail. In this project, you should at least design a class to simulate the following aspects of the self-service cash register:

·          Process the price of each purchased item (use console input from user for each item’s price)

·          Show the total purchase amount to the customer

·          Receive payment. (use console input from user for payment amount)

·          Calculate and return the change (Use console output to show the change that needs to be returned)

step 2 (5 pts.)

Specify the public interface.

Turn the list in Step 1 into a set of methods, with specific types for the parameter variables and the return values.

·          ...

·          ...

·          ...

·          ...

To complete the public interface, you need to specify the constructors. Ask yourself what information you need to construct an object of your class. Sometimes you will want two constructors: one that sets all instance variables to a default and one that sets them to user­ supplied values. In the case of the cash register example, we can get by with a single constructor that creates an empty register. A more realistic cash register might start out with some coins and bills so that we can give exact change, but that is beyond the scope of our assignment. Thus, add a single constructor:

·          ...

step 3 (10 pts.)

Document the public interface.

Use meaningful comments, that describes the class, constructors, and its methods in the JavaDoc style, using @param, @return when necessary. Make sure to update the documentation as you improve the program.

step 4 (5 pts.)

Determine instance variables.

Ask yourself what information an object needs to store to do its job. Remember, the methods can be called in any order. The object needs to have enough internal memory to be able to process every method using just its instance variables and the parameter variables. Go through each method, perhaps starting with a simple one or an interesting one and ask yourself what you need to carry out the method’s task. Make instance variables to store the information that the method needs.

·          ...

·          ...

Just as importantly, do not introduce unnecessary instance variables. If a value can be computed from other instance variables, it is generally better to compute it on demand than to store it.

step 5 (10 pts.)

Implement constructors and methods.

Implement the constructors and methods in your class, one at a time, starting with the easiest ones.

Make sure to automatically reflect the most recent item cost and the total purchase amount so far to the customer after each processed item.

Be careful, a customer might provide two separate payments, such as two $10 bills, and the machine must process them both. Remember, methods can be called more than once, and they can be called in any order. Also do not forget to reset the cash register for the next sale after you compute the change due.

If you find that you have trouble with the implementation, you may need to rethink your choice of instance variables. It is common to start out with a set of instance variables that cannot accurately reflect the state of an object. Do not hesitate to go back and add or modify instance variables.