neovim/snippets: Add java negative check

users/simon/modules/neovim/snippets.nix

@@ -73,6 +73,10 @@ let
         if (''${1:var} == null) {
             throw new NullPointerException("$1 can’t be null");
         }$0'';
+      CheckNegative = mkSnippet "chkneg" "Check for negative numbers" ''
+        if (''${1:var} < 0) {
+            throw new IllegalArgumentException("$1 can’t be negative");
+        }$0'';
     };
   };