In this lab, you will practice using exceptions and assertions.

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 The new exception should include a String message and an int that is the depth of recursion 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.

1

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 arent 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 dont include them directly as assertions in your code?