How can I make a .jar file executable?
You can always run a jar file by doing java -jar JMerise.jar.
However, to make the jar file itself executable, you need to set the executable bit, as the message hints. chmod +x /home/aimad/Programms/jMerise/JMerise.jar will accomplish this.
After that you can do ./JMerise.jar to run it.
man chmod will provide you with information about how chmod works.
Also see: https://wiki.ubuntu.com/Security/ExecutableBit
Right click on the file, click on properties, then go to the Permissions tab, and check the box that says "Allow executing this file as a program".
