SCJP Java OOP and Inheritance

Question 1

Which keyword is used in Java to prevent a class from being subclassed?

Accepted Answer

final

Answer

abstract

Answer

static

Answer

sealed

Question 2

What is the output of calling a method on an object reference declared as the superclass type but pointing to a subclass instance?

Accepted Answer

Subclass method runs due to dynamic dispatch

Answer

Superclass method runs

Answer

Compilation error

Answer

NullPointerException

Question 3

Which of the following is true about abstract classes in Java?

Accepted Answer

They can contain both abstract and concrete methods

Answer

They can be instantiated directly

Answer

They must have at least one abstract method

Answer

They cannot have constructors

Question 4

In Java, what is the result if a subclass defines a static method with the same signature as a static method in its superclass?

Accepted Answer

Method hiding occurs

Answer

Runtime polymorphism occurs

Answer

Compilation error

Answer

The superclass method is deleted

Question 5

Which access modifier allows a method to be accessed within the same package and by subclasses in other packages?

Accepted Answer

protected

Answer

private

Answer

public

Answer

default (no modifier)

Question 6

What happens when a subclass constructor does not explicitly call a superclass constructor?

Accepted Answer

The default no-arg superclass constructor is called implicitly

Answer

Compilation error always occurs

Answer

The superclass constructor is skipped

Answer

NullPointerException at runtime