Description
Objective
In this lab, you will practice using exceptions and assertions.
Working alone or in a group of 2, you will create two small programs that demonstrate how to
use exceptions and assertions.
Due: Friday, October 15, 2021 by 4pm in git at the repository
https://git.cs.dal.ca/courses/2021-fall/csci3901/lab5/???.git where ???? is your csid.
Preparation
• Review the discussion on exceptions from class.
• Review the recursive code for calculating the Fibonacci numbers from class.
• Prepare pseudocode to implement a non-recursive binary search on an array of
integers. You may get a copy from a source online for this exercise if you want.
Resources
• None required.
Procedure
Set-up
1. Get the recursive code for calculating the Fibonacci numbers working in a project.
Lab steps
Part 1 – Exceptions
1. Revise the Fibonacci code as follows to be able to limit the depth of the recursion:
o Add two parameters to the method: one to say the maximum number of levels
of recursion should be allowed and the second to say how deep you are now in
the recursion
o When the code calls itself recursively, increment the parameter on how deep
you are into the recursion
2. Create a custom-made exception called “MaximumRecursionDepth” that extends the
RuntimeException. The new exception should include a string message and an integer that
is the depth of recursion reached. Ensure that your custom-made exception has two
methods available:
o getMessage() to return the string message
o getDepth() to return the integer depth that was reached at the time of the
exception.
3. Modify your Fibonacci code to now throw a MaximumRecursionDepth exception when the
recursion depth exceeds the value of the parameter for the maximum number of levels of
recursion.
4. Modify your Fibonacci code to stop further recursive calls the first time that a
MaximumRecursionDepth exception happens.
Part 2 – Assertions
1. Write a non-recursive binary search code for an array. You can get help from the Internet
for this part; just be sure to cite any sources that you use. This step is not the critical one of
the lab.
2. Add assertions as a precondition, a loop invariant, and a postcondition to the main loop of
your binary search.
3. Ensure that your assertions are working.
Questions
• We usually want you to re-use existing code and infrastructure whenever possible. Why
might you create your own exception?
• We added parameters to the Fibonacci method. However, those parameters aren’t very
meaningful to a general user. What would you do to the code to make it more
accessible for a general user?
• How would you recommend for someone to develop a loop invariant?
• How can loop invariants help you in programming, even if you don’t include them
directly as assertions in your code?
Reporting
1. In one file, list
o The members of your team.
o The answers from the Questions section of the lab.
2. Generate a PDF from the document.
3. Submit the PDF and all your Java files in Brightspace in the Lab/Lab 4 section of the course
web page.
Assessment
The assessment will be on a letter grade and will reflect how well you implemented the
exceptions and assertions, how much you re-used existing code, and how well you demonstrate
that you can take the work of this lab and apply it to another situation (the questions section).
