OOP

Question 1

What are the two characteristics of an Object

Answer 1

State, Behaviour

Question 2

What is State

Answer 2

Fields/Variables

Question 3

What is Behaviour

Answer 3

Methods/Functions. Methods operate on an object’s internal state and serve as the primary mechanism for object-to-object communication

Question 4

What is Data Encapsulation

Answer 4

Hiding internal state and requiring all interaction to be performed through an object’s methods is known as data encapsulation

Question 5

Why use Objects?

Answer 5

1. Modularity: The source code for an object can be written and maintained independently of the source code for other objects. Once created, an object can be easily passed around inside the system.
2. Information-hiding: By interacting only with an object’s methods, the details of its internal implementation remain hidden from the outside world.
3. Code re-use: If an object already exists (perhaps written by another software developer), you can use that object in your program. This allows specialists to implement/test/debug complex, task-specific objects, which you can then trust to run in your own code.
4. Pluggability and debugging ease: If a particular object turns out to be problematic, you can simply remove it from your application and plug in a different object as its replacement. This is analogous to fixing mechanical problems in the real world. If a bolt breaks, you replace it, not the entire machine.

Question 6

What is a class?

Answer 6

A class is the blueprint from which individual objects are created.

Question 7

What is Inheritance

Answer 7

Object-oriented programming allows classes to inherit commonly used state and behaviour from other classes.

Question 8

What is superclass and subclass?

Answer 8

In the Java programming language, each class is allowed to have one direct superclass, and each superclass has the potential for an unlimited number of subclasses:

Question 9

What is the syntax of creating a subclass?

Answer 9

subclassEx EXTENDS superclassEx

Question 10

What is an Interface

Answer 10

An interface is a group of related methods with empty bodies.

Question 11

What is the syntax to use an Interface?

Answer 11

classEx IMPLEMENTS interfaceEx

Question 12

What is a Package?

Answer 12

A package is a namespace that organises a set of related classes and interfaces.

Question 13

What does API stand for?

Answer 13

“Application Programming Interface”