Overriding generic methods with non-generic implementations

Question

I\'m experimenting with generics in Java, and thought of this example.

If I have ClassA, I can override it with a subclass that references a co

Answer 1

Thanks to type erasure, this:

public <T> void doSomething(T data);

Really means this:

public void doSomething(Object data);

So no, there isn't a way to override with a more restrictive parameter type.

Also in this code:

class ClassA<T> {
    public <T> void doSomething(T data) {};
}

The type parameter in your class name and the type parameter in the method are actually different parameters. It's like declaring a local variable of the same name as a variable in a higher scope. You can call doSomething(123) on an instance of ClassA<String> because the second T is local to the method.

Answer 2

In short, the the answer is no. If you define a method with a generic parameter, then its signature contains a the generic and any "overrides" would have to match the signature (contain a generic).

Anyhow, this really is a poor use of generics, as what you've written is semantically the same as

public void doSomething(Object data) {}

The generic bit doesn't buy you much unless is it being used to indicate what the return value would be, as in:

public <T> T doSomething(T data) {}

But why bother? Is there really an issue calling doSomething() generically?