Latest comments: https://github.com/horzsolt/rigodetools/blob/master/src/main/java/horzsolt/rigodetools/mp3/Mp3Getter.java#L69 [optional] use Objects::nonNull

https://github.com/horzsolt/rigodetools/blob/master/src/main/java/horzsolt/rigodetools/mp3/Mp3Getter.java#L64 [must fix] 'return' and '{ }' is not needed

https://github.com/horzsolt/rigodetools/blob/master/src/main/java/horzsolt/rigodetools/mp3/Mp3Getter.java#L36 [codesmell] state in singleton bean

https://github.com/horzsolt/rigodetools/blob/master/src/main/java/horzsolt/rigodetools/mp3/Mp3Getter.java#L36 [must fix] use emptyList as default value instead of null that way the code will be much better in FileToMp3Mapper. You can avoid null checks (e.g.: FileToMp3Mapper.java#L119 and FileToMp3Mapper.java#L87)

https://github.com/horzsolt/rigodetools/blob/master/src/main/java/horzsolt/rigodetools/mp3/FileToMp3Mapper.java#L25 [must fix] either @Component or utility class with static methods not both

https://github.com/horzsolt/rigodetools/blob/master/src/main/java/horzsolt/rigodetools/mp3/Mp3Getter.java#L63 [optional] .map("/MP3/0-DAY/"::concat)

https://github.com/horzsolt/rigodetools/blob/master/src/main/java/horzsolt/rigodetools/mp3/Mp3Getter.java#L46 [question] is this line does anything?