setting up java on linux (debian/ubuntu)

javalinux.md

Manual install

The tar.gz provided by Oracle don't have an actual installation process. You just extract those files to a location you want and add them to your path. So the process is the following:

• Download a .tar.gz from Oracle (here I will be using jdk-8u20-linux-x64.tar.gz);
• Extract it to somewhere;
• Move the extracted folder to /usr/lib/jvm. This is not required but it is the place where Java runtime software is installed, and where tools like IDE's may search for it:

sudo mv /path/to/jdk1.8.0_20 /usr/lib/jvm/oracle_jdk8

Before addin this jdk as an alternative, you can see that the new alternative is not listed:

sudo update-alternatives --query java
sudo update-alternatives --query javac

Next, add the new jdk alternatives (2000 is the priority and feel free to pick a different number):

sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/oracle_jdk8/jre/bin/java 2000
sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/oracle_jdk8/bin/javac 2000

Now you should see the new jdk listed and you can switch between the alternatives with this command:

sudo update-alternatives --config java
sudo update-alternatives --config javac

Create a file /etc/profile.d/oraclejdk.sh with the following content (adapt the paths to reflect the path where you stored your JDK):

export J2SDKDIR=/usr/lib/jvm/oracle_jdk8
export J2REDIR=/usr/lib/jvm/oracle_jdk8/jre
export PATH=$PATH:/usr/lib/jvm/oracle_jdk8/bin:/usr/lib/jvm/oracle_jdk8/db/bin:/usr/lib/jvm/oracle_jdk8/jre/bin
export JAVA_HOME=/usr/lib/jvm/oracle_jdk8
export DERBY_HOME=/usr/lib/jvm/oracle_jdk8/db

Done! Those paths will only be recognized after you logout or restart, so if you want to use them right away run source /etc/profile.d/oraclejdk.sh.

copied from askubuntu answer. 😁