https://www.reddit.com/r/NixOS/comments/ingrvp/what_is_your_java_setup_in_shellnix/

    flake.nix
    { 
        description = "Flake to manage my Java workspace.";

        inputs.nixpkgs.url = "nixpkgs/nixpkgs-unstable";

        outputs = inputs: 
        let
            system = "x86_64-linux";
            pkgs = inputs.nixpkgs.legacyPackages.${system};
        in { 
            devShell.${system} = pkgs.mkShell rec {
                name = "java-shell";
                buildInputs = with pkgs; [ jdk11 ];

                shellHook = ''
                    export JAVA_HOME=${pkgs.jdk11}
                    PATH="${pkgs.jdk11}/bin:$PATH"
                '';
            };
        };
    }