OOP

Question 1

What is Enumeration?

Answer 1

A type of class that creates a user-defined data type

Question 2

Open Closed Principle

Answer 2

Classes can be extended, but not modified. It is violated if you will need to modify the class to handle an inheriting class

Question 3

Abstract Class

Answer 3

Cannot instantiate an object but can only be used as a base class.

Question 4

Composition

Answer 4

Form of association between classes where one class (the composite or whole) contains one of more objects of other classes (the components or parts).

Question 5

What type of relationship does composition represent? As opposed to what?

Answer 5

“Has-a” - “Is-a”

Question 6

Singleton Pattern

Answer 6

Ensures that a class has only one instance and provides a global point of access. Used when having multiple instances could lead to inconsistencies and management issues

Question 7

Abstract Factory

Answer 7

Creational design pattern. Provides an interface for creating families of related or dependent objects without specifying their concrete classes.

Question 8

Data Hiding

Answer 8

Refers to masking a classes internal operations and only providing an interface through which other entities can interact with the class without being aware of what is happening within.

Question 9

Encapsulation

Answer 9

Use to achieve data hiding. Refers to binding data and the methods to manipulate that data together in a single unit (class).

Question 10

Is it a good convention to declare all variables of a class private?

Answer 10

Yes, this restricts direct access by the code outside of the class. Use public methods such as getters and setters to grant access to internal variables.

Question 11

Abstraction

Answer 11

Technique that focuses on revealing only the necessary details of a system and hiding irrelevant information to minimize complexity.

“Show what an object does and hide how it does it”

Question 12

Polymorphism

Answer 12

Allows an object to have several different forms and behaviors.

Question 13

Dynamic Polymorphism

Answer 13

AKA runtime polymorphism. Defines methods with same name, return type and parameters in base class and derived classes. Subclasses will need to override if there is something specific it needs to do.

Question 14

Static Polymorphism

Answer 14

AKA compile-time polymorphism. Achieved by method or operator overloading.

Question 15

Operator Overloading

Answer 15

”+” can be different depending on the data type. It will concatenate a string, but add two integers

Question 16

Is static polymorphism or dynamic polymorphism more performant?

Answer 16

Static, because the binding is being done at compile time.

Question 17

Steps to drawing a sequence diagram

Answer 17

1. Identify the use case
2. Identify the Actors and Objects
3. Identify the order of actions
4. Create the diagram

Question 18

Fragment Frame

Answer 18

Allow us to represent conditional actions or loop sequences on a sequence diagram.

Question 19

Steps to drawing an activity diagram

Answer 19

1. Determine the actions of the system
2. Determine the actors and their roles, and list them out
3. Find the flow of each activity
4. Create the diagram

Question 20

Single Responsibility Principle (SRP)

Answer 20

Each class should be responsible for a single part or functionality of the system

Question 21

Open Closed Principle (OCP)

Answer 21

Software components should be open for extension but closed for modification.

A system should improve easily without changing the code core.

Question 22

Liskov Substitution Principle (LSP)

Answer 22

Objects of a superclass should be replaceable with objects of its subclasses without breaking the system

Question 23

Interface Segregation Principle (ISP)

Answer 23

Make fine-grained interfaces that are client specific

Question 24

Dependency Inversion Principle (DIP)

Answer 24

High level modules are not dependent on low-level modules.

Question 25

Creational Design Patterns

Answer 25

Used to provide a mechanism for creating objects in a specific situation without revealing the creation method.

Question 26

Structural Design Patterns

Answer 26

Concerned with class/object composition and relationships between objects. Let us add new functionalities to objects so that restructuring some parts of the system does not affect the rest.

Question 27

Behavioral Design Patterns

Answer 27

Concerned with communication between dissimilar objects in a system. Ensure information synchronization