* #2449 bump maven-checkstyle-plugin from 3.1.0 to 3.2.0 + resolve checkstyle issues
* remove FileSelectorJFrame.java to resolve checkstyle issue
* remove FileSelectorJFrame.java to resolve checkstyle issue
* remove FileSelectorJFrame.java to resolve checkstyle issue
* add refactored file with correct filename to resolve checkstyle issue
* add the test data
* change filenames from JFrame to Jframe for checkstyle
* fix code smell from sonar report
* add new testcases to improve the test coverage
* remove code smell
* #2151 add module and pom.xml
* #2151 add Calculator Actions
* #2151 add remaining mvi pattern classes (actions already implemented)
* #2151 add Main and unit tests
* add README.md and class diagrams
* #2151 add module and pom.xml
* #2151 add Calculator Actions
* #2151 add remaining mvi pattern classes (actions already implemented)
* #2151 add Main and unit tests
* add README.md and class diagrams
* fixes for lint errors
* #2151 add module and pom.xml
* #2151 add Calculator Actions
* #2151 add remaining mvi pattern classes (actions already implemented)
* #2151 add Main and unit tests
* add README.md and class diagrams
* fixes for lint errors
* use Lombok @Data decorator and decouple View from ViewModel
* add comments and documentation
* fix checkstyle, the smart switch syntax was breaking checkstyle, so I had to change it back