Mastering Java: The Ultimate Quiz for 'Thinking in Java'

Why can a generic class not directly inherit from its generic type parameter in Java?

1. Because generics in Java use type erasure

2. Because it causes a compilation error

3. Because it violates Java's type safety

4. Because of Java's inheritance rules

The correct answer is: Because of Java's inheritance rules

When a class extends a generic class, it must specify a concrete type for the generic parameter. In this case, if the generic class were to directly inherit from its generic type parameter, it would create a circular dependency and result in a compilation error. Additionally, this inheritance scenario would not make sense from a design standpoint as it would essentially create an infinite loop. Therefore, Java's inheritance rules prohibit a generic class from directly inheriting from its generic type parameter. Choices A and C are incorrect because generics in Java use type erasure, meaning that the generic type information is removed during compilation and replaced with Object as the type. Choice B is incorrect because it is a generic class inheriting from its generic type parameter that would cause a compilation error, not the other way around.