Make some of the Java classes in module-constraint proper utility classes

[vil02]

Description:

Some of the Java classes in constraint module, namely:

• Constants,
• ErrorUtils,
• Constants,
• ConstraintCompilerPluginUtils,
• CompilerPluginTestUtils,
• CompilerPluginTestConstants,

appear to be utility classes (i.e. all of the members and methods are static). Generally speaking it is a good practice to:

• explicitly mark their default constructor as private (like in ModuleUtils) - because it does not make sense to have objects of such classes,
• mark such classes as final - because it does not make sense to derive any class from them.

There are benefits of doing this:

• the design is cleaner - e.g. no one will create objects of such classes,
• the coverage report will show higher/more accurate coverage (currently it is complying that instantiation of these classes is not tested).

Suggested Labels:

module/constraint,hacktoberfest

Suggested Assignees:

@vil02

Affected Product Version:

OS, DB, other environment details and versions:

Steps to reproduce:

Related Issues:

#4894, #4901, #4902, #4910, #4911, #4918, #4919, #4921, #4923, #4926, #4927.