#2 Accept null as arguments and exceptions as return types

[Teresa Lee]

Currently, the JavaGrader only supports primitive types and arrays of primitives types for the input arguments for the test cases and primitive types for the return types for the test cases.

The following is an example of a test case that the future JavaGrader should be able to handle:

Data Type of function argument(s) if needed: int[]
Return type of function: int
Input arguments for Test Case: null
Expected Output: IllegalArgumentException

Class that will be involved in this change is the CTConverter.java.