java on linux

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This post details the steps I use to update or install the latest version of the Java Development Kit (JDK) on my Linux systems.

(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 step 1

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 and rename it jdk1.9.0:

     sudo mv ~/opt/Java/jdk-9.0.1 /usr/lib/jvm/jdk1.9.0

🔗 Make jdk1.9.0 the default Java on your system

Use the update-alternatives program for this (see also: 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.