feat (shells): haskell, java, switch to unstable

shells/java/flake.lock

@@ -0,0 +1,27 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1767116409,
+        "narHash": "sha256-5vKw92l1GyTnjoLzEagJy5V5mDFck72LiQWZSOnSicw=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "cad22e7d996aea55ecab064e84834289143e44a0",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

shells/java/flake.nix

@@ -0,0 +1,25 @@
+{
+  description = "Java nix-flake devshell.";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
+  };
+
+  outputs =
+    { self, nixpkgs, ... }:
+    let
+      system = "x86_64-linux";
+    in
+    {
+      devShells."${system}".default =
+        let
+          pkgs = import nixpkgs { inherit system; };
+        in
+        pkgs.mkShell {
+          packages = with pkgs; [
+            jdk
+            jdt-language-server
+          ];
+        };
+    };
+}