The ant dependency is only used for the excelant tasks  (which are never used in Debian ). Any use of these tasks implicitly means Ant is already on the classpath. In this context Ant can be seen as a runtime, much like the Servlet API for web based stuff. So I think it makes sense to remove the dependency from the binary package.
Splitting ant into ant+libant-java is a good idea, but this can probably wait for the Buster development cycle. Emmanuel Bourg  https://poi.apache.org/spreadsheet/excelant.html  https://codesearch.debian.net/search?q=excelant __ This is the maintainer address of Debian's Java team <http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/pkg-java-maintainers>. Please use debian-j...@lists.debian.org for discussions and questions.