A good guide:
https://www.baeldung.com/java-nio2-watchservice
https://www.codota.com/code/java/methods/java.nio.file.WatchKey/pollEvents
Generic
http://puremonkey2010.blogspot.com/2010/12/gossip-in-java-generics.html
https://www.journaldev.com/1663/java-generics-example-method-class-interface
