Class is a raw type. References to generic type Class<T> should be parameterized

Question

There are lots of threads about this type of question, but I want to get a complete answer and actually understand it without 'hiding' the problem with a @SupressWarnings !

I have the following class (from a simple Spring tutorial)

public class CarValidator implements Validator {

public boolean supports(Class aClass) {
 return Car.class.equals(aClass);
}

public void validate(Object obj, Errors errors) {
 Car car = (Car) obj;

 ValidationUtils.rejectIfEmptyOrWhitespace(errors, "model", "field.required", "Required field");

 ValidationUtils.rejectIfEmptyOrWhitespace(errors, "price", "field.required", "Required field");

 if( ! errors.hasFieldErrors("price")) {
  if (car.getPrice().intValue() == 0)
   errors.rejectValue("price", "not_zero", "Can't be free!");
 }

}

}

Where the Validator class is the org.springframework.validation.Validator class from Spring 2.5.

The supports method is showing a warning (Class is a raw type. References to generic type Class should be parameterized), if I try to add parameters to this such as

public boolean supports(Class<?> aClass) ...

I get the follwing error:

The method supports(Class) of type CarValidator has the same erasure as supports(Class) of type Validator but does not override it

I would be very grateful if someone could fully explain this please and put me out of my misery.

My applogies in advance, I've been in a 1.4 world for too long!

Answer 1

Since the interface forces you to use the raw type (i.e. doesn't allow you to specify the correct type information) you can't implement it without warnings unless you use @SupressWarnings.

The only real fix is to fix the interface (i.e. make it define boolean supports(Class<?> aClass)).

Answer 2

The interface declares the method with a raw type. In that case, you can't override it nicely without having the warning.

The origin of your problem is that the Spring interface was declared to be Java 1.4 compliant. Note that Spring 3.0 is supposed to deliver all classes as Java 1.5 compliant, so that would fix your problem. Before you upgrade, I guess you would have to live with either the warning or the @SuppressWarning.