I'm trying to execute a jar file developed in Apache NetBeans 11.2 in Ubuntu 19.10 by double clicking it or launching via terminal (java -jar filename.jar) but it doesn't launch - nothing happens. It is a simple program that manages the daily work routine of an employee, it was programmed with Jframe GUI. And the program has I / O operations. I already made the jar file executable and i have JRE installed on Ubuntu. I have discovered that the manifest file is empty and it doesn't contain the main class, instead it has: "Manifest-Version: 1.0 X-COMMENT: Main-Class will be added automatically by build" It says that the main-class will be added automatically by build but it is not added. I developed another program (a game) in Intellij Idea IDE, whose the jar file has a manifest file containing the main class and even with the fact that i have used Liberica JDK in development the Open JRE associated with jar files works.