InterviewQs

Question 1

Explain what XAMPP is

Answer 1

XAMPP is a free and open-source cross-platform web server solution stack package developed by Apache Friends. It provides a simple and lightweight way to set up a local web server environment on your computer for testing and development.

Question 2

Explain the role of XAMPP in your project

Answer 2

Local Server Environment: XAMPP simulates a live web server on your local machine, allowing you to build and test your website or web application without needing an internet connection or a live hosting service.

Question 3

What is the role of the MySQL Server

Answer 3

Data Storage: It stores all the project’s data—such as user information, product details, orders, or any dynamic content—in organized tables within databases.

Question 4

Identify and explain any 1:M relationships in your database schema

Answer 4

A 1:M (one-to-many) relationship in a database schema means that one record in a table can be associated with many records in another table.

Question 5

Show your SQL DDL & DML statements and explain

Answer 5

DDL Statements (Define the structure of the database(Create Table)), DML Statements (Insert, update, delete, or retrieve data)

Question 6

What is required for a Java program to connect to a Database

Answer 6

JDBC API (Java Database Connectivity), Database Driver (JDBC Driver), Database Server, Java Code with JDBC Logic

Question 7

What is the purpose of a Data Access Layer (Data Access Pattern)

Answer 7

Separation of Concerns, Reusability, Maintainability, Testability, Security & Validation

Question 8

What is a DTO and explain why it is necessary

Answer 8

A DTO (Data Transfer Object) is a plain Java object used to transfer data between different layers of an application. Why? Encapsulation of Data, Separation of Concerns, Security, Efficiency, Improves Maintainability

Question 9

Show your DTOs in your code and explain their structure

Answer 9

DTO’s class and structure includes Fields, Constructor, Getters/Setters

Question 10

Locate and show your range of DAO methods

Answer 10

In DAO class and show methods

Question 11

How have you included a defense against “SQL Injection”

Answer 11

A PreparedStatement is a type of SQL statement that is precompiled. PreparedStatement separates the SQL code from the input data, which is passed as parameters.

Question 12

Explain what a Result Set is

Answer 12

A ResultSet is a Java object that represents the result of a SQL query executed on a database. When you execute a query (such as a SELECT statement) through a Statement or PreparedStatement, the database returns the results of the query, which are stored in a ResultSet.

Question 13

How is a DAO related to a DTO

Answer 13

DAO: Responsible for interacting with the database and fetching or storing data.

DTO: Represents the data retrieved by the DAO, acting as a data carrier between layers of the application.

DAO uses DTO objects to transfer data between the database and the business/application logic, keeping the layers decoupled and the code more maintainable and testable.

Question 14

Should a DAO method return a “null” value – discuss the issue

Answer 14

Returning null from a DAO method is a common way to indicate that no data was found, but it has drawbacks.

Question 15

What is the Business Logic Layer

Answer 15

The Business Logic Layer is where the real-world rules and decisions of your application are enforced. It acts as a bridge between the UI and the database, ensuring the system behaves correctly and predictably.

Question 16

What is the purpose of the DAO Interface classes

Answer 16

The purpose of DAO interface classes in Java is to define a contract for how your application will interact with the database, without tying it to a specific implementation. They help enforce separation of concerns, flexibility, and testability in your application’s architecture.

Question 17

How is an interface used in the Business Object layer

Answer 17

In the Business Object Layer, an interface defines what business services are available (like registration, validation, or processing), while the implementation class defines how they work. This separation makes the application more modular, testable, and maintainable.

Question 18

Explain what a Socket is

Answer 18

A socket is an endpoint for sending or receiving data across a computer network.

Question 19

What type of data is sent on a socket

Answer 19

The type of data sent on a socket depends on the application and the protocol used (TCP or UDP), but in general, all data sent through a socket is transmitted as a stream of bytes.

Question 20

What is a Server Socket and what is its purpose

Answer 20

A Server Socket is used on the server side to listen for client connections on a specific port. It acts like a doorman, accepting connections and handing off each one to a regular Socket for communication.

Question 21

What is a Blocking I/O method, and give an example from your code

Answer 21

A Blocking I/O method is a method that waits (or “blocks”) until the operation is complete before it allows the program to continue.

Question 22

What is a Server

Answer 22

A server is a system that waits for client requests, processes them, and returns results or services.

Question 23

How do we create a Server

Answer 23

To create a server in Java, you typically use the ServerSocket class from the java.net package.

Question 24

Explain Port Numbers

Answer 24

A port number is a 16-bit integer (ranging from 0 to 65535) used to identify specific services or applications running on a machine that uses TCP/IP or UDP/IP protocols.

Question 25

What is localhost

Answer 25

Localhost refers to the local computer or device that you are currently using.

Question 26

What is a Multi-Threaded Server and what is its purpose

Answer 26

A multi-threaded server is designed to handle multiple client connections at once by assigning each connection to a separate thread. This improves performance, concurrency, and responsiveness, especially for high-traffic services. It is commonly used in applications like web servers, game servers, and chat systems.

Question 27

What is the role of the Client Handler

Answer 27

A Client Handler is a thread in a multi-threaded server that is responsible for managing communication with a specific client. It handles client requests, performs necessary actions (e.g., reading, processing, or responding to requests), and ensures the client connection is closed once communication is complete.

Question 28

How are threads used in this Client Handler

Answer 28

In the Client Handler, threads are used to process each client's request independently and concurrently. This allows the server to handle multiple clients at the same time, without blocking, ensuring non-blocking and scalable operations.

Question 29

What is a Protocol (in terms of your program)

Answer 29

A protocol in your program defines the rules for communication between the client and the server, specifying how requests and responses are structured, how errors are handled, and ensuring that both parties understand the messages being sent and received.

Question 30

Why do we need a protocol

Answer 30

A protocol is essential in client-server communication because it defines the rules and conventions for data exchange between the two systems.

Question 31

What is Serialization and Deserialization

Answer 31

Serialization and Deserialization are processes used to convert objects (usually in a program's memory) to a specific format that can be easily stored or transmitted (and vice versa).

Question 32

Why are Serialization and Deserialization necessary

Answer 32

They are essential because they allow us to efficiently store, transfer, and reconstruct complex objects across different environments and over time.

Question 33

What is JSON and why is it necessary

Answer 33

JSON (JavaScript Object Notation) is a lightweight, text-based data interchange format that's easy for both humans to read and machines to parse and generate. It is primarily used to represent structured data and is commonly used for data exchange between a server and a client, particularly in web applications.

Question 34

What alternatives are there to JSON

Answer 34

XML, YAML, Protocol Buffers

Question 35

What did you use to convert Java Objects to JSON

Answer 35

No

Question 36

What is the advantage of JSON

Answer 36

Human-readable, Lightweight and Compact, Fast Parsing

Question 37

What is Junit – explain expected and actual results

Answer 37

JUnit uses assertions like assertEquals() to compare expected and actual results, helping to determine whether the unit of code being tested works as expected. Expected Result: The predefined correct result based on the input data and the function's specification. Actual Result: The result that the method or function produces when it is executed during testing.

Question 38

What Collection classes have you used in the system – show

Answer 38

List Interface – ArrayList, LinkedList. Set Interface – HashSet, LinkedHashSet. Map Interface – HashMap, TreeMap. Stack Class – Stack.

Question 39

What is JavaFX

Answer 39

JavaFX is a framework used for building rich, interactive user interfaces (UIs) in Java applications.

Question 40

What is FXML

Answer 40

FXML is an XML-based markup language used to define the structure and layout of user interfaces in JavaFX applications.

Question 41

Explain “Dependency Injection” in FXML

Answer 41

Dependency Injection (DI) in the context of FXML refers to a design pattern used to implement loosely coupled relationships between components in an application.

Question 42

What is an Observable object and what is it used to achieve

Answer 42

An Observable object is used to track changes in its state and notify observers about those changes. This is useful for creating dynamic, interactive applications, particularly for UI elements that need to update automatically when underlying data changes.

Question 43

What is a binary stream of data

Answer 43

A binary stream of data refers to a sequence of data that is represented in binary (i.e., 0s and 1s) format and transmitted or processed as a continuous flow of bits (the smallest unit of data in computing).

Question 44

How does a Client-Server deal with the transfer of binary data

Answer 44

In a Client-Server architecture, the transfer of binary data involves sending raw byte sequences between the client and server over a network connection.

Question 45

What is a buffer and what is the right size for a buffer

Answer 45

A buffer in computing refers to a temporary memory area used to store data that is being transferred from one place to another. 8KB

Question 46

Distinguish between Git and GitHub

Answer 46

Git is the tool you use to manage version control, while GitHub is the platform that hosts your Git repositories and adds features for collaboration and project management.

Question 47

What is a Repo

Answer 47

A repo (short for repository) is a storage location where all the files related to a project are stored, along with their version history.

Question 48

What is a Git branch

Answer 48

A Git branch is a lightweight, movable pointer to one of the commits in your repository.

Question 49

Explain what code maintainability is

Answer 49

Code maintainability refers to how easily software code can be modified, updated, extended, and fixed over time. It reflects how well the codebase supports the continuous process of maintaining and evolving a software system, ensuring that developers can make changes with minimal effort, risk, and errors.