As the popular download manager JDownloader2 was not working well (gui not responding correctly, tabs not showing etc.) for me on Ubuntu 19.04, i was looking for solution. Ubuntu 19.04 comes with OpenJDK 11 and JDownloader2 uses Java 8 (Open JDK 8) , so i did the following to start JDownloader with the older (but still supported ) OpenJDK 8 version:
Install OpenJDK 8 (JRE: Java Runtine Enviroment):
sudo apt install openjdk-8-jre
System still uses OpenJDK 11 by default, you can check that with
Change the following in the script JDownloader2 in your install directory (i.e. /opt/jd2) to override the JVM (Java Virtual Machine) search sequence:
Now start JDownloader2 as usual and the program should behave normally.