Java on Linux

by William DeMeo - -

This post describes the steps I use to update or install multiple versions of the Java Development Kit (JDK) on Linux machines.

(These notes are mainly for my own reference, but also come in handy when I need to something to point to when a colleague or student needs to know how to do this.)

Download the latest JDK from Oracle

http://www.oracle.com/technetwork/java/javase/downloads/index.html

I’ll assume we’re using Linux on an x64 machine, so we would, for example, download a file with a name like jdk-9.0.1_linux-x64_bin.tar.gz. (As of Dec 6, 2018, the direct link to this file is here.)

Unpack the tar.gz file downloaded in the previous step

I’ll assume we downloaded the tar.gz file into the directory ~/opt/Java

tar xvzf jdk-9.0.1_linux-x64_bin.tar.gz

Set up the /usr/lib/jvm directory

  1. create the directory /usr/lib/jvm

     sudo mkdir -p /usr/lib/jvm

  2. If you already have directory named /usr/lib/jvm/jdk-9.0.1, move it out of the way:

     sudo mv /usr/lib/jvm/jdk-9.0.1{,.orig}

  3. Move your newly unpacked jdk directory to /usr/lib/jvm then give it the alias jdk1.9.0:

     sudo mv ~/opt/Java/jdk-9.0.1 /usr/lib/jvm/
 sudo ln -s /usr/lib/jvm/jdk{-9.0.1,1.9.0}

Make jdk1.9.0 the default Java on your system

Use the update-alternatives program to configure multiple versions of Java on the same machine. (For more details see: notes on configuring JDK 1.7 on Ubuntu):

This first block of 9 commands can be copy-and-pasted to the command line all at once:

    sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk1.9.0/bin/java" 1;
    sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/jdk1.9.0/bin/javac" 1;
    sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/lib/jvm/jdk1.9.0/bin/javaws" 1;
    sudo update-alternatives --install "/usr/bin/jcontrol" "jcontrol" "/usr/lib/jvm/jdk1.9.0/bin/jcontrol" 1;
    sudo chmod a+x /usr/bin/java;
    sudo chmod a+x /usr/bin/javac;
    sudo chmod a+x /usr/bin/javaws;
    sudo chmod a+x /usr/bin/jcontrol;
    sudo chown -R root:root /usr/lib/jvm/jdk1.9.0;

The following commands are interactive and should be invoked individually:

    sudo update-alternatives --config java
  
    sudo update-alternatives --config javac
  
    sudo update-alternatives --config javaws
  
    sudo update-alternatives --config jcontrol

Check which version of Java your system is currently using with the command java -version.

Finally, if you have other versions of Java installed on your system, you should make them available using the update-alternatives program by following the same steps as we did above for jdk version 9.0.1.