Check style Guideline

Welcome developers!

Before contributing to this project, please ensure that you have reviewed the style guidelines prior to submitting a pull request.

This guideline for IntelliJ

1. Install CheckStyle-IDE plug-in in IntelliJ

2. Go to the setting and find Code Style -> Java

3. In Scheme select Project, then Import Scheme -> Checkstyle configuration, then find the directory of the project Add checkstyle.xml, then Save