Programming Interview Questions Flashcards

Question

Describe MVP

Answer 1

Model = backend logic and data View = input begins here Presenter = processes request through the model and passes it back to the view

Answer 2

Common for Android apps, websites Suited to make views reusable

Answer 3

Model = backend logic and data View = input begins here View-Model = only purpose is maintain the state of view and manipulate the model

Answer 4

Used for mobile apps Suited to help improve performance Allows view-specific subsets of a model to be created, with the state and logic bound to the view.

Answer 5

A method used to initialise the state of an object Method is called whenever an object is created

Answer 6

A method called when the object is destroyed

Answer 7

A member function of a class Its functionality can be overridden in its derived class

Answer 8

allows you to define multiple methods in a class with the same name but with different parameter lists. Each overloaded method provides a different implementation of the same functionality

Answer 9

A class that cannot be instantiated Serves as a blueprint for other classes to inherit from

Answer 10

Equivalent to an if/else statement

Answer 11

Performs cleanup on resources not being used

Answer 12

Call by Value - value passed only modified inside function Call by Reference - value passed modified both inside and outside

Answer 13

Where a subclass’s method overrides the main class’s method. Uses same method name, parameter and type.

Answer 14

Overloading is the same method with different arguments, overriding is a different method with the same argument in a child class

Answer 15

Private Protected Public Friend Protected Friend

Answer 16

Access modifier which prevents other classes from inheriting from it.

Answer 17

Use static method

Answer 18

Structures are public by default and only stores data, classes are private and can store data and methods.

Answer 19

A function which must be overridden in the derived class, but need not be defined.

Answer 20

The degree of dependency of one class on another class; the ‘strength of relationship’ between modules. Loose coupling is usually better than tight coupling

Answer 21

Loose coupling = less interdependency, less coordination, less information flow. Classes A and B are said to be ‘loosely coupled’ if the only knowledge that class A has about class B is what class B has exposed through its interface.

Answer 22

A measure of strength of relationship between the methods and data of a class High cohesion is usually better than low cohesion

Answer 23

Allow you to add methods to existing types without creating new derived types, modifying the original code or using inheritance.

Answer 24

A static method is a method that belongs to a class rather than an instance of a class, meaning you can call a static method without creating an object of the class.

Answer 25

Mathematical operations, string manipulation methods, helper functions.

Answer 26

They are called scripts They are provided and executed as plain text, and don’t need special preparation or compilation to run.

Answer 27

Browsers have embedded engines, sometimes called a “Javascript Virtual Machine”, that: 1. Reads (parses) the script 2. Converts (compiles) the script to machine code 3. Runs the machine code.

Answer 28

A Javascript runtime environment

Answer 29

A software platform (e.g. operating system, web browser) that provides an environment for running code

Answer 30

An array is an ordered data structure that can store multiple variables of the same type. A tuple is an ordered data structure that contains a sequence of elements of different data types, and can only contain 8 elements. A list is an ordered data structure that represents a strongly typed list of objects.

Answer 31

Use nested tuples

Answer 32

An array of arrays

Answer 33

A strongly typed programming language, for example C#/python, is one in which the specification of data types is demanded. Strongly typed languages are more likely to require explicit conversion A weakly typed programming language, for example Javascript, does not require the explicit specification of different types of objects and variables, and can execute implicit type conversions at runtime.

Answer 34

Imagine comparing a string and number value. In C#, this will not compile as there’s a type mismatch. In Javascript, this code will compile and implicit conversion from the integer to a string will occur.

Answer 35

Strong typing enforces a rigid set of rules, increasing consistency Leads to faster development through detecting errors earlier and better optimised code from the compiler However, using strong typing means that a programmer may lose flexibility

Answer 36

A special program that translates a programming language’s source code into machine code (or another programming language).

Answer 37

explicit type conversion is when the programmer intentionally changes the data type of a value. Explicit conversions have a risk of losing data, e.g. when converting a double to an int. implicit type conversion is when the compiler automatically changes the data type of a value

Answer 38

An enum is a value type that represents a group of constants. Enums can be used to define options for config settings, etc.

Answer 39

Value types represent actual data values and are stored directly in memory where they are declared Reference types store ‘addresses’ to where the actual data is located in memory. When you create a variable of a reference type, the variable stores a reference to the data, not the data itself.

Answer 40

Reference types are typically stored on the heap in memory, whereas value types are stored on the stack

Answer 41

Copying a value type gives a copy of the actual data. Copying a reference type gives you a copy of the reference to the same data.

Answer 42

A normal repository implements its own specific methods for each entity type it deals with, whereas a generic repository provides a generic interface for CRUD operations that can be used with any entity type.

Answer 43

Extends capabilities of PostgreSQL relational database by adding support for storing, indexing and querying geographic data

Answer 44

A table is a structure that contains data

Answer 45

You can think of a view as a saved 'SELECT' statement that you can repeat. A view can join data from several tables.

Answer 46

All patterns provide a way to let some part of a system vary independently of other parts

Answer 47

The SOLID priniciples are: Single Responsibility Principle Open/Closed Principle Liskov Substitution Principle Interface Segregation Principle Dependency Inversion Principle

Answer 48

Each class should do one thing only and have only one reason to change.

Answer 49

Open for extension, closed for modification Open: designing components in a way that allows them to be extended or enhanced without modifying their existing code Closed: Once an entity is defined and implemented, its behavious should remain stable and not be altered Watch out for switch statements!

Answer 50

Objects of a superclass must be replaceable with objects of its subclasses

Answer 51

Code should not be forced to depend upon methods it does not use Watch out for large interfaces!

Answer 52

High-level modules should not depend on low-level modules, both should depend on abstractions.

Answer 53

Composition is a "has a" relationship, Inheritance is an "is a" relationship Composition is achieved by instantiating variables of other objects, whereas Inheritance is achieved by extended classes

Answer 54

Composition is loosely coupled Composition has access control composition is easier to unit test

Answer 55

inheritance is tightly coupled the structure of the parent is forced upon the child

Answer 56

Compile time: the period where the programming code (e.g. C#) is being converted to machine code (e.g. binary), where syntax and semantics of the code are checked Runtime: the period where a program is running (and generally occurs after compile time)

Answer 57

The repository pattern is a design pattern. It provides an abstraction layer between the business logic of an application and the data storage mechanisms.

Answer 58

What operations (methods) are supported by the repository What data (parameters) are required for each operation The repository interface contains what it CAN do, but not HOW to do it. The implementation details are in the respective repository class that implements the repository interface.

Answer 59

The Unit of Work pattern is a design pattern. It helps to maintain consistency and integrity of data operations by managing transactions and coordinating multiple database operations within a single unit of work. In the unit, either all operations succeed and are committed, or none of them are applied and they are rolled back.

Answer 60

In the context of dependency injection containers, these refer to different lifetimes of the services that the container manages Transient: these services are created each time they are requested; a new instance of the service is created each time it's resolved from the Dependency Injection container. Transient objects are always different, a new instance is provided to every controller and every service. Scoped: these services are created once per request or usage scope; this means that a single instance of the service is created and shared within the scope of a single HTTP request (in the case of web applications). Scoped objects are the same within a request, but different across different requests. Singleton: these services are created once and shared across the entire application lifetime. This means that a single instance of the service is created when it's first created, and that same instance is reused for all subsequent requests. Singleton objects are the same for every object and every request.

Answer 61

For components that need to maintain state across multiple operations within the same scope, such as database contexts in web applications.

Answer 62

For scenarios where a new instance is needed for each use

Answer 63

For stateless (no internal data that changes over time) and thread-safe components that be can shared safely across the application, such as configuration settings

Answer 64

Code cleaner and easier to maintain Enables creation of loosely coupled systems When unit testing, easy to replace a real repository with a fake implementation for testing

Answer 65

LINQ is a set of technologies based on the integration of query capabilities directly into the C# language.

Answer 66

SQL stands for 'structured query language'. SQL is used to query and manipulate the underlying relational databases, e.g. PostgreSQL

Answer 67

An open-source object-relational database system based on POSTGRES

Answer 68

An inner join is a type of join operation used in relational databases to combine rows from two or more tables based on a related column between them. The inner join selects only the rows from both tables that have matching values in the specified column(s), excluding rows where there is no match.

Answer 69

Returns all records from the left table, and matching records in the right table

Answer 70

Combines the result of left and right outer join

Answer 71

Produces the cartesian product of rows between 2+ tables

Answer 72

A primary key is a special relational database table column (or set of columns) that uniquely identifies each row in the table. It allows for efficient data retrieval, indexing and referencing between tables

Answer 73

Uniqueness Non-nullability Immutable (should not change once assigned to a record) Indexed (typically indexed by database management system for faster lookup and retrieval operations) Foreign key references

Answer 74

A foreign key is a column (or set of columns) that establishes a link between data in two tables

Answer 75

Dependency injection is a design pattern in which the dependencies of a component are provided from the outside rather than created internally. It is a technique for achieving inversion of control.

Answer 76

In traditional programming, components control the flow of execution by instantiating and invoking the methods of other components or services they depend on. Inversion of control is where the control of object creation and management is shifted from the components themselves to an external entity, typically a container or framework.

Answer 77

A container is a software component or framework that is responsible for managing the lifecycle, configuration and resolution of dependencies within an application.

Answer 78

SQL injection is a code injection technique. It is the placement of malicious code in SQL statements.

Answer 79

You can prevent SQL injection through the use of SQL parameters.

Answer 80

SQL parameters are values that are added to an SQL query at execution time

Answer 81

SQL parameters are represented in the SQL statement by an '@' marker

Answer 82

A framework is a pre-built, reusable set of libraries, tools and components that provides a foundation for developing software applications.

Answer 83

A linked list is a linear collection of data elements whose order is not given by their physical placement in memory. Instead, each element points to the next. In its most basic form, each node contains data and a reference

Answer 84

Pros: Efficient memory utilisation - size decreases or increases as per requirement Ease of insertion/deletion - no elements need to be shifted after insertion/deletion Cons: Many basic operations (such as obtaining the last node of the list) may require iterating through most or all of the list elements.

Answer 85

Can help implement data structures such as stack, queue, hash maps and graphs Can be used for navigation in web browsers

Answer 86

Arrays are of fixed size while Linked Lists are of dynamic size. Linked lists use more memory Arrays have easier access to elements Insertion and Deletion is faster for linked lists.

Answer 87

The singleton pattern is a design pattern that ensures a class has only one instance and provides a global access point to that instance. It is a creational design pattern.

Answer 88

The singleton pattern is used when exactly one instance of a class is needed throughout the lifetime of an application

Answer 89

You might need to implement the singleton pattern when managing shared resources or global configurations

Answer 90

The singleton pattern provides a way to restrict the instantiation of a class to a single object and provides a global access point to that instance. This is achieved by: Defining a private constructor to prevent external instantiation Defining a static method or property to provide access to the single instance

Answer 91

Memory efficiency: only one instance of a class can be created Lazy initialisation: allows instance to be created only when needed, improving performance and reducing startup time

Answer 92

Testing: Singleton classes can be difficult to test in isolation due to their global state and tight coupling with other parts of the application Overuse: overusing the singleton pattern can lead to code complexity and dependencies on hidden global state, making the application harder to understand and maintain.

Answer 93

Set up a private static instance variable e.g. private static readonly Singleton instance = new Singleton(); Set up a private constructor to prevent external instantiation private Singleton() { } Set up a public static property to provide access to the single instance public static Singleton Instance { get { return instance; } }

Answer 94

The Strategy Pattern is a behavioral design pattern that allows you to define a family of algorithms, encapsulate each one of them, and make them interchangeable. It lets the algorithm vary independently from clients that use it.

Answer 95

If you have a sorting algorithm that needs to be flexible enough to switch between different sorting strategies (bubble sort, quick sort, mergesort) based on different user input or user preferences

Answer 96

Flexibility: Strategies can be easily added, removed or replaced without modifying the client's code Encapsulation: each algorithm is encapsulated into its own class Testability: Strategies can be tested independently Reusability: Strategies can be reused across different contexts or applications

Answer 97

Strategy Interface: This is an interface or abstract class that defines a common interface for all supported algorithms. Concrete Strategies: These are the concrete implementations of the strategy interface Context: This is a class that uses the strategy interface to perform its operations. The context maintains a reference to a strategy object and delegates the algorithm's execution to the strategy.

Answer 98

The observer pattern is design pattern where multiple observer objects (subscribers) are notified automatically when the state of a subject object (publisher) changes

Answer 99

Define the Subject Interface: This interface defines the methods for attaching, detaching, and notifying observers. Define the Observer Interface: This interface defines the method that subjects will use to notify observers of state changes. Create Concrete Subject Class(es): These classes implement the subject interface and maintain a list of observers. They provide methods to attach, detach, and notify observers. Create Concrete Observer Class(es): These classes implement the observer interface and define the behavior to be executed in response to notifications from subjects.

Answer 100

Advantages: Loose coupling (between publishers and subscribers) Disadvantages: Performance overhead: can be performance issue if a lot of observers etc. Ordering of notifications: the order in which observers are notified of state changes is not deterministic, which can lead to unexpected behaviour.

Answer 101

Thread safety refers to the ability of a program, module, or system to perform correctly and maintain consistent behavior when accessed or manipulated by multiple threads simultaneously

Programming Interview Questions Flashcards

(126 cards)