Implement the "at the end" pairing algorithm.

[MatthewRueben]

• [x] Fix comodification error with using two Iterators over the same List.
• [x] Test some cases to ensure that the new approach works. E.g., two adjacent objects match.
• [x] Add verbose/debug mode where more stuff prints out? I.e., implement some logging.
• [x] Figure out how to specify logging level at runtime. Apparently configuration files are proper, but is there a way to easily switch to Level.DEBUG and back when there's an issue?
• [x] Move test cases to .../test/ directory? Learn to make tests. It would clean up the source files.
• [x] Design and implement a simple test.
• [x] Throw a (custom?) exception whenever no match is found for an object.
• [x] Write an additional test method to test that that exception gets thrown.

[MatthewRueben]

Brainstorm :: addressing the comodification error

• Could use a Spliterator to get an iterator over a sublist, but the documentation says not to use mutable sources.
• Could reinitialize all iterators each time a pair is removed. Could maybe do the removals outside the scope of the iterators, so they are destroyed.
• Could use recursion -- i.e., method only finds the first pair, removes them, and then passes remaining list back to itself.

[MatthewRueben]

Re: that comodification error, I ended up just using the same Iterator but reset it to the start of the List at the beginning of each outer loop. https://github.com/MatthewRueben/sock-pairing/commit/0dc2a16307845f7524aa28a898261cd92762fe47

[MatthewRueben]

Using log4j 2 for logging.

[MatthewRueben]

Sounds like programmatically setting the log4j2 logging level isn't very pretty, and the recommended thing to do is to use the configuration file. The good news is, I can use a log4j2-test configuration file that will get used for unit tests, and a log4j2 configuration file that will get used otherwise. That way I can specify two levels.

Done, and unit testing is now set up: https://github.com/MatthewRueben/sock-pairing/commit/9d779653558e4af0b3173e785ff0ec7330a4abe9

[MatthewRueben]

Re: testing that a certain exception is thrown under certain conditions, this seems to be the right answer.

[MatthewRueben]

Used this tutorial on Exceptions.

[MatthewRueben]

Ended up having my new custom NoMatchRemainingException extend RuntimeException so I don't have to check for it because this would be a user error -- namely, passing in a list of objects for which there are not 2 (or 0, 4, 6, ...) of each. 0a985bd

[MatthewRueben]

Used Assertions.assertThrows() from JUnit 5 for the test. 3685260