Whenever I change laptop or format my hard drive, I end up making a mess with the soft links to configure java...
This post is just a reminder too myself, for the future. I found a clean way I am comfortable with for setting my system to use java, via the update-alternatives tool that ubuntu has. This is how I do it:
1- Download the JDK from oracle and copy it to your user directory.
I like having it under ~/Java/jdk1.8.0_40
2- I often like installing maven, so I do the same, just I create another directory for it and I put in there the downloaded maven. ~/maven/apache-maven3.3.1
3- Then I set the necessary environmental variables for my user in the ~/.bashrc file.
4- I use update-alternatives to install in the system the java interpreter and the compiler.
sudo update-alternatives --install "/usr/bin/java" "java" "/home/djordje/Java/jdk1.8.0_40/bin/java" 1
sudo update-alternatives --install "/usr/bin/javac" "javac" "/home/djordje/Java/jdk1.8.0_40/bin/javac" 1
5- Again i use update-alternatives, but for this time to configure the default version of the interpreter and compiler to be used by default.
sudo update-alternatives --config java
sudo update-alternatives --config javac
When running the command, it shows all versions of java installed, to pick one
6- At the end I just run java -version to see that the system is using the version of java I want.
I like this way, it is easy to do and you can quickly switch to a different installed version by just using the --config option