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

All fields declared in an interface are implicitly `public static final` (constants).

Question 2

What is encapsulation in Java?

Accepted Answer

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

Answer

Encapsulation bundles data and methods together while restricting direct field access, typically using private fields and public getters/setters.

Question 3

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

Accepted Answer

false

Answer

`null instanceof AnyClass` always returns `false` without throwing an exception.

Question 4

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

Accepted Answer

Yes, with a comma-separated list

Answer

A Java class can implement multiple interfaces by listing them with commas: `class Foo implements A, B, C`.

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

A constructor shares the class name and has no return type declared (not even void).

SCJP - Sun Certified Java Programmer Practice Test