Chris,according the file list <https://packages.debian.org/sid/amd64/openjdk-8-jdk-headless/filelist> openjdk-8-jdk-headless contains /usr/lib/jvm/java-8-openjdk-amd64/src.zip
Perhaps openjdk-8-source is now obsolete? Kind regards, -- Ben Caradoc-Davies <b...@transient.nz> Director Transient Software Limited <http://transient.nz/> New Zealand