Day 1

flake.nix

@@ -0,0 +1,30 @@
+{
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+    flake-compat = {
+      url = "github:edolstra/flake-compat";
+      flake = false;
+    };
+  };
+
+  outputs = { self, nixpkgs, flake-utils, ... }:
+    flake-utils.lib.eachDefaultSystem (
+      system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+
+        millWithFixedJdk = pkgs.mill.override { jre = pkgs.jdk; };
+      in
+      {
+        devShell = pkgs.mkShell {
+          buildInputs = [ millWithFixedJdk ];
+          shellHook = ''
+            set -a
+            JAVA_HOME=${pkgs.jdk}
+            set +a
+          '';
+        };
+      }
+    );
+}