Debugging Exercise 3

Goal:

1. debug the Functions.java code.

2. Use the step over ↷ button. See the Important Tips section for more information.

Setup

From Java Bootcamp Resources -> Module 2 -> 8. Exception Handling -> Debugging Workbooks open the folder, exercise-three.

If you can't find it, please download the updated resources from Github.

Debugging

The file contains TWO functions:

1. The first function should return a random number between 1 and 15.

2. The second function should check if that number is prime or composite.

   • A prime number is not divisible by anything except itself and one (17, 29, 41...).

   • Common mistake: 1 is not a prime number.

If you run the starter code, it will crash.

Exception in thread "main" java.lang.ArithmeticException: / by zero
    at Functions.isPrime(Functions.java:15)
    at Functions.main(Functions.java:5)

Use breakpoints to visualize the runtime and debug the program line by line. Recall, you can use the step into ↓ button to step into a function.

Important Tips

1. Problem: isPrime() is called inside println(). So, how do you step inside isPrime()?

   • Solution: step into ↓ println(). Then, step out ↑ of it. The next step into ↓ will step inside isPrime().

2. Problem: When inside a method, how do you avoid stepping into other methods?

   • Solution: Use step over ↷ to execute the method without stepping in it.

Good Luck!