Clean up unnecessary constructors and constructor calls
Rename MainView.setUpCards -> setupCards
Rename PlayingCardJPanel.set* -> setup*
Rename *Test -> test* in several tests
Make variables in anonymous classes private
Remove dead code paths
Refactor to use interfaces instead of implementations for return values

e.g. returning List<X> instead of ArrayList<X>
Remove unnecessary "this"s
Remove import that should be implicit
Initialize instance variables for singletons to null
Add braces around one-line if statements
Remove unnecessary spaces before periods
Access static members through declaring type instead of subtype
Return boolean expression instead of using if-else to do the same
Fix string comparison to use !.equals() instead of !=
Make final variables that should be final
Break up long lines
Replace explicit colors with their respective color constants
Insert spaces around operators
Remove unused imports