[PDF] a super class is an incomplete class that requires further specification true or false

Should a super class be abstract?

YES, there are cases when the super class should not be abstract. At least in Java's use of the notion of abstract. Whether you make a class abstract or not is circumstantial. Abstract classes should be used when the class that you're describing is incomplete on its own. For instance: The above class represents an abstract Animal.

What is the default superclass?

Default Superclass : Except Object class, which has no superClass, every class has one and only one direct superclass (single inheritance). In the absence of any other explicit superclass, every class is implicitly a subclass of the Object class. Can you please clarify what you do not understand from the quoted text?

What is the difference between a superclass and a subclass?

Both have some advantages/disadvantages over the other: First approach (Referencing using Superclass reference): A reference variable of a superclass can be used to a refer any subclass object derived from that superclass. If the methods are present in SuperClass, but overridden by SubClass, it will be the overridden method that will be executed.

Does every class have a Super constructor?

Every class has a constructor, and every subclass constructor calls a super constructor (even if only implicitly). It sounds like the code you are describing is something like this: There are two sections of the language spec relevant to the question.