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.
Preparation
Review the discussion on exceptions from class.
Review the recursive code for calculating the Fibonacci numbers from the debugging lab. Prepare pseudocode to implement a non-recursive binary search on an array of integers.
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:
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
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 class. The new exception should include a String message and an int that is the depth of re-cursion reached. Ensure that your custom-made exception has two methods available:
getMessage() to return the string message
getDepth() to return the integer depth that was reached at the time of the exception
3. Modify your Fibonacci code to throw a MaximumRecursionDepth exception when the recursion depth exceeds the value of the parameter for the maximum number of levels of recursion.
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Part 2 - Assertions
1. Write (non-recursive) code to perform a binary search on a sorted 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 the following assertions:
a loop precondition a loop invariant
a postcondition
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 le, list
The members of your team.
The answers from the Questions section of the lab.
2. Generate a PDF from the document.
3. Submit the PDF in Brightspace and all your Java les in Brightspace in the Lab/Lab 4 section.
Assessment
The assessment will be on a letter grade and will re ect 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).
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