id3j is a lightweight and easy-to-use library to create and add ID3 metadata tags to MP3 files. It only concerns itself with ID3 version 3.2.0 and only handles the most common types of information, but creating a tag and adding it to a file is much easier than with many other solutions. It also has one fairly esoteric feature that is interesting from a algorithmical standpoint, which is the ability to create CRC32 neutral ID3 tags. That means that you can add such a tag to any MP3 file and the CRC32 sum of the resulting MP3 file with the tag will be the same as the file without the tag.
