Question

I’m using Java 1.6.0_25.

I have an annotation defined:

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface Resource {
    String value();
}

And later when I use getAnnotation:

Resource resource = (Resource)cls.getAnnotation(Resource.class);

the compiler and IDE agree that I must cast the result, but getAnnotation is declared in the Java 1.5 documentation as:

public <A extends Annotation> A getAnnotation(Class<A> annotationClass);

Since Resource.class is of type Class, it seems to me that this means that cls.getAnnotation(Resource.class) should return type Resource, and I should need to cast.

All examples I’ve found using getAnnotation don’t have a cast, so I must be doing something wrong.

Answer 1

What is the type of cls? Is it raw Class or is it Class<Something>?

If it’s the raw type Class, then the cast is necessary. If you make it at least Class<?> instead of Class, you won’t need the cast anymore.

Class cls = Example.class;

// Error: Type mismatch, cannot convert from Annotation to Resource
Resource anno = cls.getAnnotation(Resource.class);

Class<?> cls2 = Example.class;
Resource anno = cls2.getAnnotation(Resource.class); // OK

Class<Example> cls3 = Example.class;
Resource anno = cls3.getAnnotation(Resource.class); // OK