Resolve violations of IDEA inspections 2020.1.1

[Roman Ivanov]

Violations: https://teamcity.jetbrains.com/buildConfiguration/Checkstyle_ContributionIdeaInspectionsPullRequest/3854536?buildTab=Inspection

Java/Abstraction issues
'public' method with 'boolean' parameter (Errors) (1)
Java/Code maturity
Deprecated API usage (Errors) (1)
Use of System.out or System.err (Errors) (7)
Java/JUnit
JUnit test method without any assertions (Errors) (25)
Java/Naming conventions/Method
Method naming convention (Errors) (1)
Java/Performance
StringBuilder without initial capacity (Errors) (1)
Java/Portability
Call to 'System.exit()' or related methods (Errors) (1)
Java/Probable bugs
Use of Properties object as a Hashtable (Errors) (6)
Java/Resource management
AutoCloseable used without 'try'-with-resources (Errors) (7)
I/O resource opened but not safely closed (4)
Java/Verbose or redundant code constructs
Stream API call chain can be simplified (2)