I'm not sure if I am missing something but I think the code is actually
expecting digest algorithm settings like:
dnsjava.dnssec.digest.1:

public static final String DIGEST_ENABLED = "dnsjava.dnssec.digest";

while the README gives examples where _enabled is repeated in
the key itself:
Disable SHA.1: dnsjava.dnssec.digest_enabled.1=false

Thanks,