1) [Lesson #1](springboot2-junit5-skiptest/README.md) - How to write an annotation for your JUnit5 tests and to use application.properties from Spring environment
1) [Flexible Caffeine Cache Manager](flexible-caffeine-cache/FlexibleCaffeineCacheManager.java) - How to separate different cache configurations into one application using Caffeine cache
3) ['At least one group' Validator](https://gitea.bvn13.me/bvn13/JavaLessons/src/branch/master/AtLeastOneGroupValidator) - JavaX validator to check whether only one field is specified