Version mkgmap-r3686 will be last to run on java 7

All future versions of mkgmap and splitter that are downloaded from the website will require java 8 to run.

The public updates of java 7 ended over a year ago in Apr 2015 and java 8 was released in Mar 2014, so you are likely to be running java 8 already, except for some long term supported linux distributions where java 7 may still be the default and you will have to install java 8 in addition or instead of java 7.