Right now I\'m using BinaryNotes to parse ASN.1 files for use in a Java project. It takes an ASN.1 definition and produces Java class(s) that let me manipulate ASN.1 files.
Binary Notes is unsupported, but you can try jASN1 from OpenMuc. It appears to be based in part on Binary Notes and is currently active. The jASN1 libraries are available for download on their home page, and on JCenter and Maven Central under the group org.openmuc