推断Java8中Optional的泛型

Question

I'm trying to implement a method which returns an Optional of either classes: A,B,C extends Mother.

I have no idea where to start. I tried something like this

    private Optional<U> get(String query,U u){
    }

A = c.get("Looking for an A",A.class)
B = c.get("Looking for an B",B.class)
C = c.get("Looking for an C",C.class)
C = c.get("Looking for an k",k.class) // Exception, K doesn't extend `Mother`

Answer 1

Almost there, here's a better version.

private <U extends Mother> Optional<U> get(String query, Class<U> clazz) {
    ...
}

The bounded type parameter makes sure can only pass a subclass of Mother (or Mother.class itself).