How to install GUI on your ubuntu server?

sudo apt-get install ubuntu-desktop

Increase speed of your JDownloader on Ubuntu

change your jdownloader.desktop under /usr/share/applications


[Desktop Entry]
Name=JDownloader
Categories=Network;FileTransfer
Exec=java -jar /home/eric/.jdownloader/JDownloader.jar -Dsun.java2d.opengl=true
Icon=jdownloader
Terminal=false
Type=Application

original is just jdownloader