I have a little application for drawing phrase structure trees that was written in Java, in roughly 2013. The author included a launch script, and it runs fine on Xubuntu 22.04.3, but on Sparky Linux I get:
$ ./TreeForm_launch_script Error: could not open `/usr/lib/jvm/jdk-21-oracle-x64/lib/jvm.cfg' There is a document, also written in 2013, stating that it needed JRE 1.42 or later. Such is not available for SparkyLinux, but it wasn't available in Xubuntu either. The default in SparkyLinux is Debian 17, and I installed jre-8u381-linux-x64 and both jdk17 and jdk21, all downloaded from Oracle. I assume they are 'installed' correctly, because LibreOffice needs a JRE for some functions, and it has a utility to choose which java it is supposed to use; and all four appear in the list of available javas. I have no idea what the above error message means, and less than that about how to fix it. I know zero about such matters. Can someone hit me over the head with a clue?
