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Java: Pass a class that extends X and implements X [duplicate]

I want to have a Class object, but I want to force whatever class it represents to extend class A and implement interface B.
I can do:
Class<? extends ClassA>
Or:
Class<? extends InterfaceB>
but I can't do both. Is there a way to do this?

Actually, you can do what you want. If you want to provide multiple interfaces or a class plus interfaces, you have to have your wildcard look something like this:
<T extends ClassA & InterfaceB>
See the Generics Tutorial at sun.com, specifically the Bounded Type Parameters section, at the bottom of the page. You can actually list more than one interface if you wish, using & InterfaceName for each one that you need.
This can get arbitrarily complicated. To demonstrate, see the JavaDoc declaration of Collections#max, which (wrapped onto two lines) is:
public static <T extends Object & Comparable<? super T>> T
max(Collection<? extends T> coll)
why so complicated? As said in the Java Generics FAQ: To preserve binary compatibility.
It looks like this doesn't work for variable declaration, but it does work when putting a generic boundary on a class. Thus, to do what you want, you may have to jump through a few hoops. But you can do it. You can do something like this, putting a generic boundary on your class and then:
class classB { }
interface interfaceC { }
public class MyClass<T extends classB & interfaceC> {
Class<T> variable;
}
to get variable that has the restriction that you want. For more information and examples, check out page 3 of Generics in Java 5.0. Note, in <T extends B & C>, the class name must come first, and interfaces follow. And of course you can only list a single class.

You can't do it with "anonymous" type parameters (ie, wildcards that use ?), but you can do it with "named" type parameters. Simply declare the type parameter at method or class level.
import java.util.List;
interface A{}
interface B{}
public class Test<E extends B & A, T extends List<E>> {
T t;
}

How do I declare a class that implements an interface that constrains the type of a class?

I've seen examples of how to declare a generic class whose type parameter is constrained, e.g. it must extend Comparable. I also know how to define an interface for a generic class whose type is similarly constrained. However, when I do the latter, I'm unable to figure out the syntax for the class signature. So, to cut a long story short, if the interface is
public interface iMyClass<T extends Comparable<T>>
what should be the syntax for the signature for the implementing class
public class MyClass.......
Thanks in advance,
D

Do you intend MyClass to be generic as well? If so,
public class MyClass<? extends Comparable<T>> implements iMyClass<T> {
Otherwise, keep things simple and
public class MyClass implements iMyClass<String> {
Replace String with your Comparable.

A constrained type argument is supplied in exactly the same way as a non-constrained one, for instance:
public class MyClass implements iMyClass<String> {

Force Interface Method Return Value to be Wildcard with Multiple Classes

This question is a follow up from Java Generics Wildcarding With Multiple Classes.
I'm writing an interface like this:
public interface SomeInterface {
public Class<? extends SomeClass implements OtherInterface> getClassForObject(Object object);
}
I know that this is wrong syntax, as is Class<? extends SomeClass & OtherInterface>, and it seems all options.
I can't have the interface do what was suggested in the answer to the question linked above (public interface SomeInterface<T extends SomeClass & OtherInterface>) because implementations of this interface might want to return different things for different inputs.
I also can't create an abstract class that extends SomeClass and implements OtherInterface and have everything extend from that because there are many existing implementations of SomeClass that clients may want to extend from.
Is there any way to force implementations of this interface to return a type that fits both constraints? Besides throwing a runtime exception somewhere else in the code?

You cannot impose multiple restrictions on a wildcard. You can declare a generic type parameter on the method instead of the interface itself, and you can impose multiple restrictions on it. Try:
public interface SomeInterface {
public <T extends SomeClass & OtherInterface> Class<T>
getClassForObject(Object object);
}

What does <R extends TableRecord<R>> mean in Java?

I'm creating an interface of JOOQ TableRecord
<R extends TableRecord<R>>
Would anyone be able to explain the line above?
Thanks

It means a class of type R, that implements the interface TableRecord<R>
TableRecord<R> means that the interface is bound to the same type R.
An example would be a class like:
public class Bla implements TableRecord<Bla>
I admit this seems a bit strange, but Java generics don't really differentiate between extends and implements, which leads to some confusion.
As to why this exact definition, I don't know enough about the context to see exactly why it makes sense, but it might be due to method signatures on the interface returning objects of type R (think Factory):
public R createTableRecord(...);

class SomeClass<R extends TableRecord<R>>
What it means that parameter type R has to be a subclass of TableRecord <R> and nothing else, i.e. you must use class
class Foo extends TableRecord <Foo>
as the parameter for defining your class SomeClass

How to restrict types which are allowed as "T" in a generic class?

I've got a class Foo<T>. How can I say that I want T to be some class implementing BarInterface? Writing simply class Foo<T implements BarInterface> doesn't compile.

Use extends instead of implements.