Machine-applicable refactorings

[petervdonovan]

I did a quick (< 2 hour) pass through some files related to the C generator because the warnings appearing in the IDE were distracting. The only changes that should make any semantic difference to our code are replacement of == with .equals to compare strings.

In the interest of minimizing conflicts (and of avoiding controversy), I tried to do this quickly and neglected many more potential issues that IntelliJ flagged. Maybe some more "code health" passes of this sort should happen if we think it's a good idea.

Changes include:

• Replacing redundant type arguments with diamond types
• Removing redundant toString() calls in string concatenation
• Using pattern matching to avoid casting (after using instanceof)
• Fixing broken references in Javadoc comments
• Deleting or updating outdated method documentation
• Replacing usages of == and != to compare strings! This seems like a real bug, and it surprises me that it was not caught in CI.

Changes do not include:

• Removing unnecessary parentheses
• Always surrounding + with spaces when used for string concatenation
• Making members final
• Deleting unused class variables
• Deleting unused methods
• Deleting unused parameters
• Deleting useless local variables
• Addressing warnings that point to logical errors in the control flow of methods
• Addressing "wrong tag" warnings for comments of the form "@author{Name Surname [email protected]}" that make "@author{Name" look like all one JavaDoc tag
• Refactoring "pseudo functional style code" that causes side effects, even though it uses APIs designed for functional programming

[lhstrh]

The uppercase is a bit weird here. I'd write osn or something like that.

[lhstrh]

Thanks for these cleanups!