Since java 9 some java programs have been broken. They very cleverly changed a lot of things in Java 9 which broke many many programs, especially those that use plugins using the URLClassLoader.
So many people still need to run Java 8 on their system, and they miss out on the joys of running newer Java implementations, like Java 11. That is, unless they manually change programs to point directly to a specific java version.
Java Selector is a small Perl program which replaces /usr/bin/java on your system
(usually using the update-alternatives system) and examines the command line passed
to it. If it finds a .jar file anywhere in the command line it compares it to a
list of files held in /etc/java-mappings. If it finds it in there it gets the
java version to run for that file.
That found java executable, if any, is then called with the existing command line arguments untouched. If no mapping is found it uses the "default" java installation.
This means you can just maintain one central list of mappings for your java programs and have it automatically run the right version of Java for you.
Requires IPC::System::Simple:
$ sudo apt-get install libipc-system-simple-perl
Then just run:
$ sudo make install
To activate the selector either go through your normal update-alternatives interface,
or run:
$ sudo update-alternatives --set java /usr/bin/java-selector
You can add new mappings by editing (as root):
/etc/java-mappings
That file contains a list of file = command pairs:
/path/to/jar/file.jar = /path/to/executable/bin/java
For example:
/usr/share/uecide/uecide.jar = /usr/lib/jvm/java-8-openjdk-amd64/bin/java
/usr/share/filebot/FileBot.jar = /usr/lib/jvm/java-8-openjdk-amd64/bin/java