unchecked generics usage warning on getAllClassMetadata() instance method of org.hibernate.SessionFactory

I just cant understand this. I'm calling

AnnotationConfiguration annotationConfiguration = new AnnotationConfiguration();
SessionFactory sessionFactory = annotationConfiguration.configure().buildSessionFactory();
Map<?, ?> allClassMetadata = sessionFactory.getAllClassMetadata();

Well, the only way I don't have warning is if I'm using wildcard ? But! if I look at definition of getAllClassMetadata() method in the SessionFactory interface or any of it's implementation the returning type is Map<String,ClassMetadata>. So, the problem is. When I write

Map<String,ClassMetadata> allClassMetadata = sessionFactory.getAllClassMetadata();

Eclipse tells me The expression of type Map 开发者_开发知识库needs unchecked conversion to conform to Map<String,ClassMetadata> I just don't get this. It's dumb. Please help.

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This javadoc link says getAllClassMetadata() returns a Map