Object oriented programming

Question 1

Define class

Answer 1

The definition of the attributes and methods of a group of similar objects

Question 2

Define attributes

Answer 2

The properties that an object if that type has, implemented using variables

Question 3

Define methods

Answer 3

Processes or actions that an object of that type can do, implemented with subroutines

Question 4

Define object

Answer 4

A specific instance of a class

Question 5

Define instantiation

Answer 5

The process of creating an object based in its class definition

Question 6

What is a constructor

Answer 6

A special method that is called when the object is instantiated

Question 7

What is the relationship between an object and its class?

Answer 7

An object is an instance of the class

Question 8

What is encapsulation?

Answer 8

The concept of grouping similar attributes, data and methods together in one object

Question 9

What is information hiding?

Answer 9

Controlling access to other data stored within an object

Question 10

State the name, symbol and meaning for the three main access specifiers

Answer 10

• Private: Cannot be accessed from any other object
  + Public: Can be accessed from any object
  # Protected: Can only be accessed from this object or an object of this class/ subclass

Question 11

What is grouped together in encapsulation?

Answer 11

Attributes
Methods
Data

Question 12

What are the advantages of encapsulation?

Answer 12

Makes program more modular
Makes debugging easier
Allows programming tasks to be split between different programmers
Prevents access to certain attributes or methods from other objects

Question 13

How is it possible for private attributes to be accessed by other objects?

Answer 13

Getters and setters which are public methods that can access private attributes

Question 14

What is inheritance?

Answer 14

The idea that a class can use the attributes and methods defined in another class

Question 15

What is a subclass?

Answer 15

A class that inherits the attributes and methods from another class

Question 16

What is a base/parent class?

Answer 16

A class whose attributes and methods are inherited by another class

Question 17

What are the benefits of inheritance?

Answer 17

Same code can be reused without the need to copy it
If code needs changing it only needs to be changed in the base class
Less chance of errors
Easier to debug

Question 18

What is aggregation?

Answer 18

The idea that one class can be related to another using a ‘has a’ relationship

Question 19

What is a container class?

Answer 19

A class or object that contains or is made up of other objects

Question 20

Describe the two types of aggregation

Answer 20

Association aggregation: Aggregation where the container object can be destroyed without destroying it’s associated objects

Inheritance aggregation: Aggregation where, if the container object is destroyed then all associated objects are destroyed

Question 21

What is an associated class/object?

Answer 21

A class/object that is used to make up another object

Question 22

What is the difference between inheritance and aggregation?

Answer 22

Inheritance is an ‘is a’ relationship, aggregation is a has a relationship

Question 23

Define polymorphism

Answer 23

The ability for two methods with the same name to carry out their actions using different code

Question 24

Define overriding

Answer 24

A method in a subclass re-defining a method inherited from a bass class

Question 25

How can a computer identify which method to run if there are two methods with identical identifiers in that class?

Answer 25

Comparing the number and type of the arguments

against the expected parameters of each method

Question 26

What is an interface?

Answer 26

A collection of subroutines that can be implemented by unrelated classes

Question 27

What are the advantages of using OOP?

Answer 27

OOP more closely resembles the real world relationships between objects
Easier to debug
Classes can be reused in other code
Code can be reused through inheritance and aggregation

Question 28

What are abstract methods?

Answer 28

A method that has no program code and is intended to be overwritten

Question 29

What are virtual methods?

Answer 29

Methods that may be overwritten (default in some languages)

Question 30

What are static methods?

Answer 30

Methods in a class that can be called without the need to create an object of that class

Question 31

What should be included in a detailed class diagram?

Answer 31

Class names
Attributes
Methods
Data types
Access specifiers
Relationships