For Ubuntu 22.04, you should be able to simply:
sudo apt install openjdk-21-jdk
It's in the Universe repository, so be sure you have that enabled.
It wasn't available yet when you asked the question, but it is now.
If you add a PPA or other non-Ubuntu version of OpenJDK, remember that it's likely to be incompatible with the (supported Ubuntu repository) Ubuntu package. So keep track of what you install; you might need to remove all of it.
Answer from user535733 on askubuntu.comHow can i install Java 21 on Debian 12 without resorting to sid?
Trying to install jdk 21. But it says already on the newest
How to install Java?
Installing Java on Arch
Videos
EDIT: I've ended up installing Microsoft's OpenJDK 21. Had a nice instructions to setup and i didnt need to mess up my debian repositories to get the thing (only add MS one). Sorry die-hard Linux fans
I'm trying to install the JRE of Java 21 in my Debian 12 headless machine, for Minecraft server purposes.
Unfortunately i saw that the packages of 21 aren't available in stable repositories, only on sid (unstable). I don't want to add the whole sid repository to avoid instability and since the only package i want is this one.
So, is there any way to install Java 21 using either apt or a .deb file - without resorting to unpack a .tar.gz? Should i download the .deb on the website and try to install it via gdebi-core? I read that this isn't an advised thing to do due to dependencies and such...