Because core.jar is an executable java
archive, it is possible to start GroIMP just by
(double-)clicking on the file in your system’s file browser as
you would do it with a usual executable file. This requires a
suitable setup of your file browser, see the documentation of
the browser and your Java installation if it does not already
work.
You can set up your desktop to show a menu entry for GroIMP. How this is done depends on your system. Usually your system provides a menu editor where you can create a new menu entry and specifiy the command to be executed when the entry is activated. Choose the command as you would do on command line.
The file core.jar in your installation
directory of GroIMP’s binary distribution is the entry-point
for starting GroIMP. Running GroIMP from the command line is
easy:
java -jar path/to/core.jar
Of course, path/to/core.jar has to be
replaced by the actual path to the file
core.jar. E.g., if, on a Unix system, the
installation directory is /usr/lib/groimp,
the command would be
java -jar /usr/lib/groimp/core.jar
or, on a Windows system with installation directory
C:\Program Files\GroIMP,
java -Xverify:none -jar “C:\Program Files\GroIMP\core.jar”