Ultimate Guide to Crack Java Full Stack Developer Interviews in 2025

Step-by-Step Preparation Strategy

1. Master Core Java Concepts

• Grasp OOP fundamentals (Abstraction, Encapsulation, Inheritance, Polymorphism)
• Understand multithreading, collections, exception handling
• Dive into JVM internals, memory management, garbage collection

2. Deep Dive into Spring Boot & Microservices

• Create REST APIs using Spring Boot
• Learn Spring Security, Spring Data JPA, Validation
• Explore Microservices architecture, Eureka, API Gateways

3. Get Comfortable with Frontend Frameworks

• Master JavaScript (ES6+), TypeScript
• Practice building responsive UIs with Bootstrap or Material UI

4. Sharpen Your Database Skills

• Write complex SQL queries, understand joins and indexing
• Learn NoSQL with MongoDB – schema, queries, indexing
• Understand transactions, ACID properties, stored procedures

5. Understand DevOps & Cloud Basics

• Learn Docker and Kubernetes (basic deployment and orchestration)
• Get hands-on with CI/CD tools like Jenkins, GitHub Actions
• Practice deploying apps on AWS (EC2, Lambda, S3, RDS)

6. Work on Real Projects

• Build 2–3 full stack apps with frontend/backend integration
• Deploy them using Docker or cloud services
• Showcase on GitHub or personal portfolio

7. Prepare for the Interview

• Practice mock interviews
• Keep your resume clean, project-oriented, and keyword-rich
• Follow tech trends via blogs, GitHub, and newsletters

100 Most Common Java Full Stack Interview Questions (Topic-Wise)

Core Java – 20 Questions

1. What are the pillars of OOP in Java?
2. Difference between == and .equals()
3. What is method overloading and overriding?
4. How does garbage collection work?
5. What are Checked and Unchecked exceptions?
6. Explain HashMap vs Hashtable
7. What is the use of final, finally, and finalize()?
8. Explain synchronized keyword
9. What is the JVM and how it works?
10. Difference between ArrayList and LinkedList
11. What are lambda expressions?
12. Explain Stream API
13. What is autoboxing and unboxing?
14. What is the Singleton Pattern?
15. Functional interface and examples
16. What is Java Reflection API?
17. Compare == and compareTo()
18. Explain multithreading in Java
19. How does HashSet work internally?
20. What is the difference between System.out.println() and Logger?

Spring Boot & Microservices – 20 Questions

1. What is Spring Boot? How is it different from Spring?
2. What are annotations like @RestController, @Service?
3. How does dependency injection work?
4. What is the use of application.properties?
5. How do you handle exceptions globally in Spring?
6. Explain @Autowired vs constructor injection
7. What is Spring Security and how to configure JWT?
8. Difference between @Component, @Bean, and @Configuration
9. What is Spring Data JPA?
10. How to implement pagination and sorting?
11. What are Microservices?
12. Explain API Gateway
13. What is Service Discovery?
14. What is Circuit Breaker in Microservices?
15. How does OpenAPI/Swagger work in Spring Boot?
16. What is Feign Client?
17. How do microservices communicate?
18. What is Load Balancer in Microservices?
19. What is Spring Cloud Config?

Frontend (React/Angular) – 15 Questions

1. What is Virtual DOM in React?
2. Explain React Hooks – useState, useEffect, useContext
3. Class components vs Functional components
4. What is Redux and how does it work?
5. What are Angular Directives?
6. Explain two-way data binding in Angular
7. How does state and props work in React?
8. Explain lifecycle methods in React
9. What is lazy loading in Angular?
10. What is RxJS and why is it important?
11. Form validation in Angular
12. Differences between Angular and React
13. What is Webpack and Babel?
14. How to manage large state in React apps?
15. What is SPA (Single Page Application)?

Databases (SQL & NoSQL) – 15 Questions

1. Difference between SQL and NoSQL
2. What is Normalization?
3. What are indexes and when to use them?
4. How to write JOIN queries (INNER, LEFT, RIGHT)?
5. Difference between WHERE and HAVING clauses
6. What are transactions and ACID properties?
7. Stored Procedures vs Triggers
8. How to optimize slow SQL queries?
9. What is MongoDB and how is data stored?
10. How do you implement relationships in MongoDB?
11. What is the difference between find() and aggregate()?
12. Explain MongoDB indexing
13. How to use schema-less design effectively?
14. What is a Foreign Key?
15. How do you design a scalable DB schema?

DevOps & Cloud – 10 Questions

1. What is Docker and how do you containerize an app?
2. What is Kubernetes?
3. What is CI/CD pipeline?
4. What is Jenkins and how does it work?
5. What is AWS EC2 and how do you use it for deployment?
6. Explain S3 and its use cases
7. Difference between ECS and EKS
8. What is Infrastructure as Code (IaC)?
9. How to deploy Spring Boot apps using Docker?

Git & Version Control – 5 Questions

1. Difference between Git and GitHub
2. What is git pull vs git fetch?
3. How do you resolve merge conflicts?
4. What is .gitignore?
5. How do you create and switch branches?