Java

Installation

Install Oracle JDK 9 (considered stable in 3/2018)

su -
add-apt-repository ppa:webupd8team/java
apt-get update
apt-get install oracle-java9-installer
emacs /etc/environment
 JAVA_HOME="/usr/lib/jvm/java-9-oracle"

# needed?  apt-get install oracle-java9-set-default
ctrl-D (back to user)
update-alternatives --config java # make note of path
update-alternatives --config javac # make note of path
sudo subl /etc/environment
JAVA_HOME="/usr/lib/jvm/java-8-oracle/jre/bin/java" # actually, use the path from above, of course