While looking at https://bugs.openjdk.java.net/browse/JDK-8190312 we noticed that:
The javadoc tool recommends http: instead of https:
(and http: doesn't actually work with the jdk9 javadoc)
and the same applies to the javadoc.1 files in the jdk10 mercurial repo.
... and of course the internet industry is moving towards https: as the default