Java Basic to Advance programes 🧑‍💻

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List of topics you need to cover if you're preparing for Java Interviews based on current Job market:

1. Core Java Fundamentals (Refer to already posted topics)
2. Advanced Java
- Design Patterns
- Multithreading
- Java Memory Model
- Performance Optimization
- Reflection & Dynamic Proxies
3. Spring Framework
- Spring core concepts
- Spring boot
- Spring Data JPA
- Spring Security
- Spring cloud
- Spring webflux
4. Hibernate
5. Testing (JUnit, Mockito, Integration, Functional, Performance Testing)
6. Build Tools (Maven / Gradle)
7. Logging
8. RDBMS, NoSQL DBs
9. WebSecurity Concepts
10. REST API concepts
11. CI/CD (Jenkins, GitHub Actions)
12. Containerization (Docker, Kubernetes)
13. Version Control (GitHub)
14. Monitoring (Grafana, ELK Stack etc)
15. Cloud (AWS, Azure, GCP (Very rare) )
16. Spring boot microservices
16. Messaging systems
17. Caching Strategies
18. System Design
19. Data Structures
20. Algorithms
21. Agile Methodologies
22. Behavioral questions

🏆 – Java Developer

Stage 1 – Java Basics (Syntax, Data Types, Variables)
Stage 2 – Object-Oriented Programming (OOP)
Stage 3 – Exception Handling
Stage 4 – Java Collections Framework
Stage 5 – File I/O
Stage 6 – Multithreading and Concurrency
Stage 7 – Java Streams and Lambda Expressions
Stage 8 – JDBC
Stage 9 – Servlets and JSP
Stage 10 – Spring Framework Basics
Stage 11 – Spring Boot
Stage 12 – RESTful APIs with Spring
Stage 13 – Testing
Stage 14 – Deployment
Stage 15 – Build projects

Typical java interview questions sorted by experience


Junior
* Name some of the characteristics of OO programming languages
* What are the access modifiers you know? What does each one do?
* What is the difference between overriding and overloading a method in Java?
* What’s the difference between an Interface and an abstract class?
* Can an Interface extend another Interface?
* What does the static word mean in Java?
* Can a static method be overridden in Java?
* What is Polymorphism? What about Inheritance?
* Can a constructor be inherited?
* Do objects get passed by reference or value in Java? Elaborate on that.
* What’s the difference between using == and .equals on a string?
* What is the hashCode() and equals() used for?
* What does the interface Serializable do? What about Parcelable in Android?
* Why are Array and ArrayList different? When would you use each?
* What’s the difference between an Integer and int?
* What is a ThreadPool? Is it better than using several “simple” threads?
* What the difference between local, instance and class variables?

Mid
* What is reflection?
* What is dependency injection? Can you name a few libraries? (Have you used any?)
* What are strong, soft and weak references in Java?
* What does the keyword synchronized mean?
* Can you have “memory leaks” on Java?
* Do you need to set references to null on Java/Android?
* What does it means to say that a String is immutable?
* What are transient and volatile modifiers?
* What is the finalize() method?
* How does the try{} finally{} works?
* What is the difference between instantiation and initialisation of an object?
* When is a static block run?
* Why are Generics are used in Java?
* Can you mention the design patterns you know? Which of those do you normally use?
* Can you mention some types of testing you know?

Senior
* How does Integer.parseInt() works?
* Do you know what is the “double check locking” problem?
* Do you know the difference between StringBuffer and StringBuilder?
* How is a StringBuilder implemented to avoid the immutable string allocation problem?
* What does Class.forName method do?
* What is Autoboxing and Unboxing?
* What’s the difference between an Enumeration and an Iterator?
* What is the difference between fail-fast and fail safe in Java?
* What is PermGen in Java?
* What is a Java priority queue?
* *s performance influenced by using the same number in different types: Int, Double and Float?
* What is the Java Heap?
* What is daemon thread?
* Can a dead thread be restarted?

Source: medium.

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