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Java Full-Stack Developer Interview Questions

May 24, 2022
Posted by: Pavithra
Category: Interview Question and Answers

Top Full Stack Developer Interview Questions and Answers

1. What is Full Stack development?

Java Full-Stack Developer Interview Questions : Full Stack development involves developing both the front end and back end of the web application/website at the same time. This process includes three layers:

Presentation layer (frontend part responsible for user experience)
Business logic layer (backend part refers to the server-side of the application)
Database layer

2. What do Full Stack Web Developers do?

A Full Stack Web Developer is a person who is familiar with developing both client and server software. In addition to mastering CSS and HTML, they are also know how to program browsers, databases, and servers.

To fully comprehend the role of Full Stack developer, you must understand the web development components – front end and back end

The front end comprises a visible part of the application in which the user interacts, while the back end includes business logic.

3. Name a few Full Stack developer tools?

Some of the popular tools used by full-stack developers to make development more accessible and efficient are:

Backbone
Visual Studio Code
WebStorm
Slack
Electron
TypeScript
CodePen
GitHub

4. What skills do you need to be a full-stack developer?

A Full Stack developer should be familiar with:

Basic languages – Must be proficient in basic languages like HTML, CSS, and SQL.
Front-end frameworks – BootStrap, AngularJS, VueJS, ReactJS, JavaScript, TypeScript, Python, Ruby, PHP
Back-end frameworks – Express, Django, NodeJS, Ruby on Rails
Databases – MySQL, SQLite, Postgres, MongoDB, Cassandra, Apache storm, Sphinx
Additional skills recommended – Git, Machine Learning, SSH, Linux Command, Data Structures, Character encoding.

5. Explain Pair Programming?

As the name suggests, Pair Programming is where two programmers share a single workstation. Formally, one programmer at the keyboard called the “driver” writes the code. The other programmer is the “navigator” views each line of the code written, spell check, and proofread it. Also, programmers will swap their roles every few minutes and vice-versa.

6. What is CORS?

Cross-origin resource sharing (CORS) is a process that utilizes additional HTTP headers to tell browsers to provide a web application running at one origin. CORS accesses various web resources on different domains. Web scripts can be integrated using CORS when it requests a resource that has an external origin (protocol. Domain, or port) from its own.

7. What is Inversion of Control (IoC)?

Inversion of Control (IoC) is a broad term used by software developers for defining a pattern that is used for decoupling components and layers in the system. It is mostly used in the context of object-oriented programming. Control of objects or portions of a program is transferred to a framework or container with the help of Inversion of Control. It can be achieved using various mechanisms such as service locator pattern, strategy design pattern, factory pattern, and dependency injection.

8. State difference between GraphQL and REST (Representational State Transfer).

For decades, REST (Representational State Transfer) has been a popular architectural way to design APIs (Application Programming Interfaces), but the popularity of GraphQL over the past few years threatens to topple REST. In general, REST and GraphQL both aim to transfer data over internet protocols including HTTP. How they do so differs greatly, however.

GraphQL	REST
It is a Query Language for APIs that enables declarative data fetching to provide clients control over which data to retrieve from the API.	It is an API design architectural style that defines a set of constraints to create web services.
GraphQL is known for its high predictability. With this, you can send requests to your API and get the exact results you are looking for without having to include anything you don’t need. GraphQL queries give predictable results, which improves their usability significantly.	On the other hand, REST’s behaviour depends on the HTTP and URI methods used. API consumers can therefore be unsure of what to expect when calling an endpoint.
API security can be ensured by GraphQL, though the security features aren’t as mature as those of REST. GraphQL, for instance, assists in integrating data validation, but users are left to figure out how to apply authentication and authorization measures.	API security can be enforced in several ways using REST. You can implement multiple methods of API authentication, such as HTTP authentication, to ensure REST API security.
With GraphQL, you can retrieve everything you need through a single API request. You can specify the structure of the information you need, and the server will return the same structure to you, so there is no need to over-and under-fetch.	Consequently, since REST APIs have rigid data structures that return the specified data whenever they are accessed, you may end up with unwanted data or have to make multiple requests before getting the right data. As a result, the server’s response time (to return information) can be prolonged due to these shortcomings.
It only supports JSON format.	XML, YAML, JSON, HTML, and other formats are supported, as well.
The main use cases of GraphQL are mobile applications and multiple microservices.	Rest is mainly used for simple applications and resource-driven applications.

9. What is CI (Continuous Integration)?

CI (Continuous Integration), as its name implies, is the process of automating and integrating code changes into a single software project, often several times a day. The purpose of this DevOps practice is to enable developers to merge their code changes into a central repository where automated tests and builds can run. Automated tools are used to assert the new code’s correctness before integration. A source code version control system is the crux of the CI process. The version control system is also supplemented with other checks like automated code quality tests, syntax style review tools, and more.

Advantages:

Integrating regularly has the main benefit of detecting errors quickly and more easily. Since most changes introduced are small, pinpointing the specific change that caused a defect is easy.
As a result of the smaller code changes and easier fault isolations, CI reduces MTTR (Mean Time to Resolution).
When CI is incorporated into your organization’s development process, you are less likely to have noncritical defects on your backlog. Before production, these small defects are detected and fixed before they are released to the public.

10. Explain the meaning of multithreading.

The thread is an independent part or unit of a process (or an application) that is being executed. Whenever multiple threads execute in a process at the same time, we call this “multithreading”. You can think of it as a way for an application to multitask.

Advantages:

By multithreading, computing resources are also minimized and used more effectively.
The response time of the application is improved since requests from one thread do not block requests from other threads.
Consequently, if one of the threads encounters an exception, it will not affect the other threads.
Multithreading, on the other hand, uses fewer resources than running multiple processes simultaneously.
The overhead, time usage, and management associated with creating processes are much higher when compared to creating and managing threads.

12. What are some of the uses of Docker?

One of the thorniest problems in software development is dealing with the different environments across different machines and platforms. Using Docker, you can isolate your applications from your infrastructure, which is crucial to delivering software quickly. Developers can package and run their applications into containers, executable components that have all the OS (Operating System) libraries and dependencies needed to run the application in any environment. It does not matter what is installed on the host—containers are lightweight and include everything needed to run applications.

The code has to pass through many different environments as it travels from the developer’s machine to production. Consequently, each of these environments may be slightly different. Using Docker streamlines code development and deployment, as it provides a consistent environment from development to production.
Docker’s primary purpose is to simplify configuration. With VM (Virtual Machine), you can run any platform with its configuration on top of your infrastructure. Docker offers the same functionality without the overhead of virtual machines.

14. Is there a way to decrease the load time of a web application?

Here are some ways to reduce load times for web applications:

Image Optimization: The file size of an image can be dramatically reduced by switching to a different file format. For example, GIFs work well for images with few colors, such as logos, JPEG is ideal for images with lots of colors and details, such as photographs, and PNG format is ideal for transparent images with high quality.
Keep JavaScript and CSS in external files: Embedding JavaScript and CSS in HTML documents forces them to be downloaded every time the HTML document is loaded. In this case, browser caching is not utilized, and the HTML document becomes larger. This is why you should always place CSS and JavaScript in external files; it is a best practice and simplifies maintenance.
Reducing redirects: Too many redirects will delay the loading time of a website. HTTP requests and responses are delayed each time a page redirects. Getting rid of unnecessary redirects on your site will reduce the load time of your site significantly.
Load CSS and JavaScript files asynchronously: Your website contains CSS and JavaScript files that can be loaded either synchronously or asynchronously. As part of synchronous loading, each file is loaded sequentially, in the order it appears on your site. As opposed to synchronous loading, asynchronous loading allows multiple files to be loaded simultaneously, boosting the performance of a website.
Minify HTML, CSS, and JavaScript: If you optimize the way your files load, your pages will load more quickly. You can do the same when it comes to HTML, CSS, and JavaScript code. By eliminating unnecessary spaces, characters, and comments, you can reduce the size of your files. This will make your web pages load faster.

Full Stack Developer Interview Questions for Freshers

15. What is Dependency Injection?

Dependency Injection is a design pattern by which IoC is executed. Injecting objects or connecting objects with other objects is done by container instead of by the object themselves. It involves three types of classes.

Client class: It depends on the service class.
Service class: It provides service to the client class.
Injector class: It injects service class objects into the client class.

16. What is Continuous Integration?

Continuous Integration (CI) is a practice where developers integrate code into a shared repository regularly to detect problems early. CI process involves automatic tools that state new code’s correctness before integration. Automated builds and tests verify every check-in.

17. What is multithreading and how it is used?

The main purpose of multithreading is to provide multiple threads of execution concurrently for maximum utilization of the CPU. It allows multiple threads to exist within the context of a process such that they execute individually but share their process resources.

18. How is GraphQL different from REST?

This is typically a difficult question to answer, but a good developer will be able to go through this with ease. The core difference is GraphQL doesn’t deal with dedicated resources. The description of a particular resource is not coupled to the way you retrieve it. Everything referred to as a graph is connected and can be queried to application needs.

19. List the ways to improve your website load time and performance.

There are quite a lot of possible ways to optimize your website for the best performance:

Minimize HTTP requests.
Utilize CDNs and remove unused files/scripts.
Optimize files and compress images.
Browser caching.
Apply CSS3 and HTML5.
Minify JavaScript & Style Sheets.
Optimize caches.

20. What is the Observer pattern?

The purpose of the Observer pattern is to define a one-to-many dependency between objects, as when an object changes the state, then all its dependents are notified and updated automatically. The object that watches on the state of another object is called the observer, and the object that is being watched is called the subject.

21. What’s the difference between Full Stack Engineer and Full Stack Developer?

A Full-Stack engineer is someone with a senior-level role with the experience of a Full Stack developer, but with project management experience in system administration (configuring and managing computer networks and systems).

22. What is polling?

Polling is a method by which a client asks the server for new data frequently. Polling can be done in two ways: Long polling and Short Polling.

Long polling is a development pattern that surpasses data from server to client with no delay.
Short polling calls at fixed delays and is based AJAX-based.

23. What’s the difference between GET and POST?

The following table compares the GET and POST:

GET	POST
GET is used to request data from a specified resource.	POST is used to send data to a server to create/update a resource.
Can be bookmarked	Cannot be bookmarked
Can be cached	Not cached
Parameters remain in the browser history	Parameters are not saved in the browser history
Data is visible to everyone in the URL	Data is not displayed in the URL
Only ASCII characters allowed	Binary data is also allowed

Full Stack Developer Interview Questions for Experienced

24. What’s the difference between abstract and interface?

The following table compares the abstract and interface:

Abstract	Interface
An abstract class can have abstract and non-abstract methods	The interface can have only abstract methods.
An abstract class can have static, non-static, final, non-final variables.	The interface has only static and final variables.
An abstract class can provide the implementation of the interface.	Interface can’t provide the implementation of an abstract class.
An abstract class can be extended using the keyword “extends”.	An interface can be implemented using the keyword “implements”.
A Java abstract class can have class members like private, protected, etc.	Members of a Java interface are public by default.

25. How can you prevent a bot from scraping a publicly accessible API?

If the data within the API is publicly accessible, then it’s not possible to prevent data scraping completely. However, there is an effective solution that will deter most people/bots: rate-limiting (throttling).

Throttling will prevent a specific device from making a defined number of requests within a defined time. Upon exceeding the specified number of requests, 429 Too Many Attempts HTTP error should be thrown.

Other possible solutions to prevent a bot from scrapping are:

Blocking requests based on the user agent string
Generating temporary “session” access tokens for visitors at the front end

26. What is RESTful API?

REST stands for representational state transfer. A RESTful API (also known as REST API) is an architectural style for an application programming interface (API or web API) that uses HTTP requests to obtain and manage information. That data can be used to POST, GET, DELETE, and OUT data types, which refers to reading, deleting, creating, and operations concerning services.

27. What is a callback in JavaScript?

A callback in JavaScript is a function passed as an argument into another function, that is then requested inside the outer function to make some kind of action or routine. JavaScript callback functions can be used synchronously and asynchronously. APIs of the node are written in such a way that they all support callbacks.

28. What do you mean by data attributes?

Data Attributes are used to store custom data private to the application or page. They allow us to store extra data on the standard, semantic HTML elements. The stored data can be used in JavaScript’s page to create a more engaging user experience.

Data attribute consists of two parts:

Must contain at least one character long after the prefix “data-” and should not contain uppercase letters.
An attribute can be a string value.

29. What’s the difference between “resetting” and “normalizing” CSS?

Resetting	Normalizing
Removes all the built-in browser styling.	Normalizing makes elements render consistently across browsers.
Provides bug fixes	Includes bug fixes

30. What does ACID mean in Database systems?

Acronym ACID stands for Atomicity, Consistency, Isolation, and Durability. In database systems, ACID refers to a standard set of properties that ensure database transactions are processed reliably.

31. How is rolling deployment different from blue-green deployment?

In a rolling deployment, a new version of the application gradually replaces the previous one. Upgrading the system takes a period of time, and both old and new versions will coexist without affecting user experience or functionality in that phase.
In a blue-green deployment, two identical production environments work in parallel. One is a blue environment that runs the production environment by receiving all user traffic. Another one is the green environment which you want to upgrade. Both use the same database backend and app configuration. If you swap the environment from blue to green, then traffic is directed towards a green environment.

32. What is an Application server?

An application server is a software framework that allows the creation of both web applications and server environments. It contains a comprehensive service layer model and supports various protocols and application programming interfaces (API).

33. What is referential transparency?

Referential transparency is a term used in functional programming to replace the expression without changing the final result of the program. This means that whether the input used is a reference or an actual value that the reference is pointing to the program’s behavior is not changed.

34. What are the differences between Server-side Scripting and Client-side Scripting?

Basis for comparison	Server-side scripting	Client-side scripting
Definition	Works in backend and not visible to the client-side.	Works in frontend and scripts are visible among users.
Processing	Server Interaction required	Interaction with the server is not required
Languages	Ruby on Rails, PHP, ASP.net, Python, ColdFusion, etc.	CSS, HTML, JavaScript, etc.
Security	Relatively Secure	Insecure

35. What are the types of design patterns?

In general, a design pattern is a repeatable solution for common problems occurring in software design. These patterns show the interactions and relationships between classes and objects.

Mainly, there are three types of design patterns:

Creational – These are about object creation or class instantiation. Further, these patterns are categorized into object-creational patterns and class-creational patterns.
Structural – These are about organizing different classes and objects to form larger functionality and provide new functionality.
Behavioral – These are about identifying common communication patterns between objects.

36. What’s the difference between normalization and denormalization?

Normalization	Denormalization
Normalization is used to reduce data redundancy and data inconsistently from the table.	Denormalization is used to add redundancy to execute queries.
Data integrity is maintained	Data integrity is not maintained
In normalization, no of tables is increased.	In denormalization, no of tables is decreased.
Normalization optimizes the usage of disk space.	Denormalization does not optimize the disk spaces.

37. Name a few ways to optimize a website to be as efficient and scalable as possible?

The following ways are used to optimize website:

Optimize all assets
Enable gzipping
Defer parsing of JavaScript
Avoid inline JavaScript, CSS, and duplicate code
Reduce DNS lookups
Serve scaled images
Specify image dimensions
Minimize request size
Leverage browser caching

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