Get instance of Class<T> [Runtime-Type Token]

Question

I create a Preferences class and for the Getters I wan't to use Runtime-Type Token.

So here is my getter method:

public <T> T get(String key, Class<T> clazz) {
    // do some crazy stuff (e.g. Double <-> Float)
}

Up to that, everything works fine. But I would like that the class parameter will be optional.

boolean b = preferences.get(key);

So I add an additional method:

public <T> T get(String key) {
    // return get(key, Class<T>);
}

Now the Question: Is there a way to do that? Is there a way to get an/the instance of Class<T>.

It's possible with a small workaround:

public <T> T get(String key, T... args) {
    return get(key, (Class<T>) args.getClass().getComponentType());
}

public <T> T get(String key, Class<T> clazz) {
    System.out.println("key  : " + key);
    System.out.println("clazz: " + clazz);
}

// using
Boolean b = get("mykey");

Answer 1

You can't. But if you want to class parameter to be optional, simply pass null and check if it's not null when you use it.

If you want to infer it from the left-hand side - it's not possible.