It uses Lazy.nvim as the plugin manager, lspconfig for the language server configuration, none-ls for formatting, telescope, tree-sitter and many other plugins. Partially documented and fairly well organized

Issues with jdtls

Ensure you have jdk21-opnejdk or newer installed. On Arch (and derivatives) you can switch the preferred java version using archlinux-java set <version name>

Fixing the errors in Java files

Copy the pom.xml file to the root of your project, then run mvn dependency:resolve to download the support files