SCJP Java OOP and Inheritance 3

Question 1

Which statement about Java interfaces is correct for SCJP?

Accepted Answer

Interface fields are public static final by default

Answer

Interface methods are private by default

Answer

Interfaces can extend multiple classes

Answer

Interface constructors are optional

Question 2

What is encapsulation in Java?

Accepted Answer

Hiding implementation by restricting direct access to fields and exposing via methods

Answer

Extending classes to reuse code

Answer

Implementing multiple interfaces

Answer

Overriding methods in subclasses

Question 3

What does the `instanceof` operator return when the reference is null?

Accepted Answer

false

Answer

true

Answer

NullPointerException

Answer

Compilation error

Question 4

In Java, can a class implement more than one interface?

Accepted Answer

Yes, with a comma-separated list

Answer

No, only one interface is allowed

Answer

Only if interfaces share a common parent

Answer

Only in Java 8+

Question 5

Which of the following correctly defines a constructor in Java?

Accepted Answer

It has the same name as the class and no return type

Answer

It has a return type of void

Answer

It must call super() explicitly

Answer

It cannot be overloaded

Question 6

What is the effect of marking a class member as `private`?

Accepted Answer

Accessible only within the declaring class

Answer

Accessible within the package

Answer

Accessible by subclasses only

Answer

Accessible everywhere