CSCI 4448/5448 — Fall 2012

I spent time today implementing the program specified by Homework 3 to be in a better place for answering student questions. It's a fun program to write.

While implementing my solution, I found it helpful to place checks on the number of videos currently rented by a customer. I did the following:

													  public void incrementRented() {
													    numberOfVideosRented++;
													    if (numberOfVideosRented > 3) {
													      System.out.println("ERROR: Customer " + name + " has more than 3 videos.");
													      System.exit(1);
													    }
													  }
													
													  public void decrementRented() {
													    numberOfVideosRented--;
													    if (numberOfVideosRented < 0) {
													      System.out.println("ERROR: Customer " + name + " has less than 0 videos.");
													      System.exit(1);
													    }
													  }
													

This is an example of two things: implementing a class invariant and failing fast.

• The class invariant is that a customer should always have between 0 and 3 videos rented inclusive.
• Failing fast is printing out an error message and calling System.exit() to end the program as soon as the invariant is broken.

Applying this strategy allowed me to find bugs in my customer types as soon as they did something weird, such as rent 4 videos at once.

Finally, if you would like to see an example of the type of output your program can produce, take a look at the output generated by my program. Note: your output doesn't have to look exactly like this as long as it contains the items requested by the problem statement; plus, only the final report at the end of my output is required. (I found it helpful to print out the activity of each day and night, but that's not required.)

Hope this helps and have fun implementing your own solution!

The slides for Lecture 10 are now available. The sample code for Lecture 10 is also available! Also, on a side note, we are now finished with one third of the semester!

The slides for Lecture 9 are now available.

Details on Homework 3 are now available. Don't forget to upload Homework 2 before the lecture starts today and in-class students should bring a printout of Homework 2 to class. Also, don't forget about Quiz 1. Be sure to take it before 11:59 PM tomorrow!

Since the Ball and Socket notation is not well supported in modern tools, the best replacement is the technique I used in Lecture 7 shown on slide 40 and reproduced below. The "ball" get replaced by two classes, one tagged with «Interface» to show what interface is being referenced/used, the second class is the one that is implementing the interface. This is shown via an association that has been tagged with the UML stereotype «implements». The "socket" is then replaced by a simple association between the class that makes use of the interface and the interface itself.

In the diagram below, the "ball" is the pair of classes named DelegateInterface and Delegate and the "socket" is represented by the association between Host and DelegateInterface.

Feel free to ignore the ball and socket notation and just use this one for the rest of the class.

One of our more industrious and forward thinking students, Chis Sterling, contacted me to share an approach he has used in the past to study for his midterms. That approach is to have the students in a class collaboratively edit a document to contain the most important concepts covered in class and to document any examples I use to explain those concepts that don't appear on the lecture slides.

The resulting document can serve as a resource when studying for the midterm and a reminder about what I said were likely questions that will appear on the midterm.

I think this is a terrific idea and so I'm happy to share the following URL that points to a Google document that Chris has started for this purpose:

https://docs.google.com/document/d/1Z7tSODfNrrgD6T5wZyMK7zF5jWf5j-Bl0qczG_Zt7nE/edit

Feel free to edit this document during lecture and/or to enter information from past lectures that you think will be useful for studying for the midterm.

The sample code for Lecture 7 and Lecture 8 is also available.

Quiz 1 is now on the Moodle. It will become active at 4 PM MDT on Saturday, September 15th (i.e. in roughly 15 minutes from the time this post appears) and will stay active until 11:59 PM MDT on Friday, September 21st.

You are allowed one attempt at the quiz, so make sure you are in a situation where you will not be interrupted and that you have access to all of the course material (i.e. lecture slides, your notes, and the textbook).

I will remind you to take the quiz several times this week. It's up to you to take the quiz before it closes on Friday night. If you miss the quiz, you miss it. It will not be reopened after it closes.

The slides for Lecture 6 are now available.

The slides for Lecture 5 are now available.

Reminder: Homework 1 is due tomorrow. You should make sure you upload a .zip archive by 12:25 PM tomorrow containing a PDF file with answers to questions 1-3 and a folder containing the source code that you wrote for question 4.

For in-class students, bring a printout of your answers to questions 1-3 AND a printout of your source code as well.

For students who worked in teams: First, THANK YOU! Second, please upload only ONE submission to the moodle for the entire team. (Just make sure all of your team members are listed on the first page of your PDF document.) Third, please bring only ONE printout of your work to class. Since you worked as a team, you will also grade as a team. You should plan on sitting together in lecture.

See you all tomorrow!

With respect to the designs that you need to create in Homework 1, let Chapter 1 of the textbook be your guide with respect to the amount of detail these designs need to have. You do not need to generate a bunch of information for these designs, just high level overviews that provide the basic structure of the design.

I have created a new section of the website that will host the sample code reviewed in class. I have also uploaded the sample code associated with Lecture 2. I just barely had a chance to review some of that code in lecture, last Thursday. I will spend more time reviewing all of it in Lecture tomorrow.