public <T> T fromJson(String json, Class<T> classOfT) throws JsonSyntaxException {

try {
    goodGson.fromJson(badJson, User.class);
} catch (JsonSyntaxException e) {
    System.out.println("Good deserializer caught JsonSyntaxException");
}

Gson badGson = new GsonBuilder()
          .registerTypeAdapter(User.class, new UserBadDeserializer())
          .create();

class UserBadDeserializer implements JsonDeserializer<User> {
    @Override
    public User deserialize(JsonElement json, Type typeOfT, 
                         JsonDeserializationContext context) throws JsonParseException {
        JsonObject jsonObject = json.getAsJsonObject();
        if (!jsonObject.has("name")) 
                     throw new JsonParseException("json should contain the name field!");
        String name = jsonObject.get("name").getAsString();
        return new User(name);
    }
}

        try {
            try {
                badGson.fromJson(badJson, User.class);
            } catch (JsonSyntaxException e) {
                System.out.println("Good deserializer caught JsonSyntaxException");
            }
        } catch (RuntimeException e) {
            System.out.println("Bad deserializer didn't catch JsonSyntaxException, and " 
                        + e.getClass().getSimpleName() + " flew further");
        }