Pre-Install sudo apt-get install software-properties-common https://packages.ubuntu.com/zh-tw/trusty/software-properties-common Install Oracle Java8 sudo add-apt-repository "deb http://ppa.launchpad.net/webupd8team/java/ubuntu xenial main" sudo apt-get update sudo apt-get install oracle-java8-installer javac -version Install Oracle Java9 sudo apt-get install oracle-java9-installer Java version manager sudo update-alternatives --config java SET JAVA_HOME Modified ~/.profile vim ~/.profile Append JAVA_HOME to environment # JAVA_HOME JAVA_HOME="/usr/lib/jvm/java-8-oracle" # JAVA version manange controller aliases alias jvc='sudo update-alternatives --config java' Verify source ~/.profile echo $JAVA_HOME jvc jerry@local:~$ jvc There are 2 choices for the alternative java (providing /usr/bin/java). Selection Path Priority Status ------------------------------------------------------------ 0 /usr...