Full Stack Java Interview Questions for Fresher with Answers

Fullstack development refers to working on both the frontend (client-side) and backend (server-side) of a web application. Fullstack developers manage the UI/UX, business logic, databases, and server configurations, offering end-to-end solutions.

2.What is the role of a Fullstack Java Developer?

A Fullstack Java Developer works on both the client-side and server-side of an application using Java for backend logic, databases for storage, and frontend technologies like HTML, CSS, and JavaScript for the user interface.

3.What are some popular Java frameworks used in Fullstack development?

Common Java frameworks for fullstack development include Spring (for backend), Hibernate (for ORM), and Spring Boot (for microservices). On the frontend, developers often use frameworks like Angular, React, or Vue.js.

4.What is Spring Framework?

Spring Framework is a powerful Java framework for developing enterprise applications. It provides a wide range of modules like Spring MVC for web applications, Spring Boot for microservices, and Spring Data for database interactions.

5.What is Spring Boot?

Spring Boot is an extension of Spring Framework that simplifies the development of standalone applications and microservices. It provides auto-configuration and embedded servers, allowing developers to quickly deploy applications.

6.What is Hibernate?

Hibernate is a Java ORM framework that maps Java objects to database tables. It simplifies database operations by abstracting SQL queries, making it easier to work with databases in a Java application.

7.What is JPA (Java Persistence API)?

Java Persistence API (JPA) is a specification in Java that defines how to manage relational data in applications using ORM. Hibernate is one of the most popular implementations of JPA.

8.What is RESTful web services?

RESTful web services are API services that follow the REST (Representational State Transfer) architecture. They use HTTP methods like GET, POST, PUT, and DELETE to perform CRUD operations on resources represented by URIs.

9.What is SOAP web services?

SOAP (Simple Object Access Protocol) is a messaging protocol that allows programs running on different platforms to communicate via XML-based web services. It is more structured and secure than REST but heavier in terms of performance.

10.What is the difference between REST and SOAP?

REST is lightweight, stateless, and uses multiple formats like JSON or XML, while SOAP is XML-based and provides built-in security and transaction management. REST is more flexible, whereas SOAP is more reliable for enterprise-level systems.

11.What is Dependency Injection (DI) in Spring?

Dependency Injection (DI) in Spring is a design pattern where dependencies (objects) are provided to a class by an external framework (Spring). It makes the code more modular, testable, and reduces tight coupling between components.

12.What is an MVC architecture?

The Model-View-Controller (MVC) is a design pattern where the application is divided into three components: Model (data), View (UI), and Controller (business logic). Spring MVC is a common implementation for Java web applications.

13.What is Thymeleaf?

Thymeleaf is a Java template engine used to render HTML, XML, and other formats in Spring web applications. It is commonly used to build dynamic views and integrates seamlessly with Spring MVC.

14.What is microservices architecture?

Microservices architecture divides an application into smaller, independent services that can be developed, deployed, and scaled independently. Spring Boot is commonly used to build microservices in Java.

15.What is Docker?

Docker is a tool that allows developers to package applications and their dependencies into containers. These containers ensure the application runs consistently across different environments, making it easier to deploy and scale applications.

16.What is Kubernetes?

Kubernetes is an open-source platform for managing containerized applications across multiple hosts. It automates the deployment, scaling, and operation of application containers, often used in conjunction with Docker.

17.What is Continuous Integration (CI)?

Continuous Integration (CI) is a practice where developers integrate their code into a shared repository multiple times a day. Each integration is verified by automated builds and tests to detect issues early.

18.What is Continuous Deployment (CD)?

Continuous Deployment (CD) refers to automatically releasing updates to production after code changes pass the necessary automated tests and quality checks. It enables frequent, reliable releases.

19.What is a build tool in Java?

A build tool automates the process of compiling, testing, and packaging code. Common Java build tools include Maven and Gradle, which help manage project dependencies and configurations.

20.What is Maven?

Maven is a popular Java build tool used for project management and dependency management. It uses an XML file called pom.xml to manage project configurations, dependencies, and build lifecycle.

21.What is Gradle?

Gradle is another build automation tool for Java and other languages. Unlike Maven, it uses a Groovy or Kotlin-based DSL, offering more flexibility and control over the build process.

22.What is an API Gateway?

An API Gateway acts as a reverse proxy that handles all incoming API requests and routes them to the appropriate microservices. It manages authentication, rate limiting, and logging, providing a single entry point for multiple services.

23.What is JWT?

JSON Web Token (JWT) is a compact and self-contained token used for authentication between a client and server. It consists of header, payload, and signature, and is commonly used in securing RESTful web services.

24.What is OAuth2?

OAuth2 is an authorization framework that allows applications to grant limited access to user resources on another service, without exposing credentials. It is commonly used in securing APIs and managing user permissions.

25.What is NoSQL?

NoSQL databases provide a flexible and scalable approach to handling unstructured or semi-structured data. Unlike SQL databases, NoSQL solutions like MongoDB, Cassandra, and Redis do not rely on relational table structures.

26.What is MongoDB?

MongoDB is a NoSQL database that stores data in JSON-like documents. It is known for its scalability, flexibility, and ability to handle large volumes of unstructured data.

27.What is SQL injection?

SQL Injection is a security vulnerability where an attacker inserts malicious SQL code into a query to manipulate or access the database. Properly sanitizing inputs and using prepared statements can prevent SQL injection attacks.

28.What is JUnit?

JUnit is a popular Java testing framework used to write and run unit tests. It allows developers to ensure that individual components of the application work as expected.

29.What is Mockito?

Mockito is a Java mocking framework used for unit testing. It allows developers to create mock objects for testing purposes, ensuring components can be tested in isolation from dependencies.

30.What is SOLID in software design?

SOLID principles are a set of design principles that help developers build maintainable, extensible, and scalable systems. They include Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, and Dependency Inversion principles.

31.What is the difference between GET and POST in HTTP?

GET requests retrieve data from the server and are typically used for read-only operations. POST requests send data to the server, commonly used for creating or updating resources.

32.What is CORS?

Cross-Origin Resource Sharing (CORS) is a mechanism that allows web servers to specify allowed origins for cross-origin requests. It prevents unauthorized access to resources from different domains, enhancing security.

33.What is WebSocket?

WebSocket is a communication protocol that provides full-duplex communication between a client and a server over a single, long-lived connection. It is used for real-time applications like chat, games, and live feeds.

34.What is asynchronous programming?

Asynchronous programming allows code to run in non-blocking mode, improving performance by allowing other tasks to execute while waiting for operations (like I/O) to complete. Java supports asynchronous programming using CompletableFuture and ExecutorService.

35.What is Lambda Expression in Java?

Lambda expressions in Java provide a concise way to represent anonymous functions. They are used primarily in functional programming and can simplify the implementation of interfaces with a single abstract method (SAM), like Runnable.

36.What is the Stream API in Java?

Java Stream API allows developers to process sequences of elements in a functional style. It provides operations such as filter, map, and reduce, enabling efficient data processing in collections.

37.What is the default method in Java?

Default methods in Java are methods with a default implementation in an interface. They were introduced in Java 8 to allow interfaces to evolve without breaking existing implementations.

38.What is polymorphism?

Polymorphism in Object-Oriented Programming (OOP) is the ability to present the same interface for different data types or classes. In Java, polymorphism is achieved through method overloading and method overriding.

39.What is inheritance?

Inheritance in Java allows one class to acquire the properties and behaviors of another class. It promotes code reuse and establishes a parent-child relationship between classes.

40.What is encapsulation?

Encapsulation in Java is the concept of wrapping data (variables) and code (methods) together as a single unit. It restricts direct access to certain components, enhancing data security and modularity.

41.What is abstraction in Java?

Abstraction is the process of hiding implementation details from the user and only exposing essential features. In Java, it is achieved using abstract classes and interfaces.

42.What is an interface in Java?

An interface in Java is a reference type that can contain only abstract methods and constants. It provides a way to achieve abstraction and multiple inheritance in Java.

43.What is a constructor in Java?

A constructor in Java is a special method used to initialize objects. It has the same name as the class and does not have a return type. Constructors can be default or parameterized.

44.What is exception handling?

Exception handling in Java is a mechanism to handle runtime errors and ensure the program does not crash. It is achieved using try, catch, finally, throw, and throws blocks.

45.What is the difference between checked and unchecked exceptions?

Checked exceptions are exceptions that must be handled at compile time (e.g., IOException), while unchecked exceptions (e.g., NullPointerException) occur at runtime and do not need to be explicitly handled.

46.What is garbage collection in Java?

Garbage collection is the process of reclaiming memory used by objects that are no longer referenced in a Java program. The JVM automatically performs garbage collection, freeing memory resources.

47.What is multithreading in Java?

Multithreading in Java is a feature that allows concurrent execution of multiple parts of a program (threads). It is useful for performing tasks simultaneously, improving performance and responsiveness.

48.What is synchronization in Java?

Synchronization is a mechanism in Java that ensures thread safety by controlling the access of multiple threads to shared resources. It prevents race conditions and ensures consistency in multithreaded programs.

49.What is a servlet?

A servlet is a Java class used to create web applications by handling HTTP requests and responses. It runs on a server and is a key component of Java’s server-side programming.

50.What is JSP?

JavaServer Pages (JSP) is a technology that allows developers to create dynamic web content by embedding Java code directly into HTML pages. JSP simplifies the creation of web applications with dynamic data rendering.