Question

I have a super class with a signature like

public abstract class Foo<C extends Comparable<? super C>>{..}

So the C class is supposed to be a Comparable object.

I want to use org.joda.time.Instant (version 1.6) as the type parameter in a subclass

public class SubFoo<Instant>

unfortunately i get this error:

Bound mismatch: The type Instant is not a valid substitute for the bounded parameter <C extends Comparable<? super C>> of the type BigtablePoller<T,C>

The Instant class extends AbstractInstant which implements Comparable (no type parameters)

Is there any way around this issue?

The only way i have been able to make it work is to change Foo to:

@SuppressWarnings("rawtypes")
public abstract class Foo<C extends Comparable> {}

I would like to avoid the warning and Josh Bloch says not to use raw types in new code (effective java Item 23).

Answer 1

Joda time 1.6 doesn’t support Generics so there are three options.

1. Create a wrapper class that implements the correct interface and use that.
2. Suppress Warnings on the super class and deal with the uglyness
3. upgrade to joda time 2.0 which supports the generic comparable interface on Instant.