You can do it without gson, solely with json in a simple way, like this:

JSONArray jsonArray = new JSONArray(Files.readString(Paths.get("path/to/your/file.json"))); // This way it always works with the newest data in that file

for (Object element : jsonArray) {
    JSONObject jsonObject = (JSONObject) element;
    // You can now work with jsonObject, in your example, the cars
}