Hi @deimantasgaizauskas,

So, there can be a few reasons behind the experienced issues. Firstly, make sure you’ve covered the proper tutorial for installing Java on Debian. It’s full of unreliable sources. In this case DigitalOcean have a pretty good article on how to install Java https://www.digitalocean.com/community/tutorials/how-to-install-java-with-apt-on-debian-9 .

Having said that in the tutorial it’s not mentioned how to exactly install Java11 only up to Java10 so after you follow the initial configuration steps, to install Java11 you should be able to perform the following

• Get the proper repo

echo 'deb http://ftp.debian.org/debian stretch-backports main' | sudo tee /etc/apt/sources.list.d/stretch-backports.list

• Make an update

sudo apt update

• Install Java11

sudo apt install openjdk-11-jdk

Now, if you still are experiencing issues, here comes the second bug I can think of. Since you mentioned you have Java8 installed and everything works fine with it, are you sure that when you install Java11 you are not still using the Java8 binaries? Java11 and Java8 do have different paths and as such the binaries located for them are also in different folders.

Regards,
KDSys