Tag: java

When I start preparing for company switch. I was confused should I prepare from the basics or should I more focus on the important topics. And based on my last 6 years of experience I can definitely suggest that, No need to start from basics. Focus more on the important topics. And below I have categorized important topics that you must prepare before your next interview. Core Java Topics (You should have a solid grasp on these): OOP Concepts: Inheritance, Polymorphism, Encapsulation, Abstraction. Example-based questions on inheritance, method overriding/overloading, encapsulation, and abstract classes/interfaces. Exception Handling: Difference between checked and unchecked exceptions. try-catch-finally block, throw vs. throws. Custom exceptions: How to create and use them. Handling multiple exceptions, multi-catch and try-with-resources (for AutoCloseable resources). Collections Framework: List, Set, Map interfaces, and their implementing classes (like ArrayList, HashSet, HashMap). Thread-safe collections like ConcurrentHashMap and CopyOnWriteArrayList. Collections utility class, sorting, filtering, and transformation operations. Streams and Lambda Expressions (Java 8+): Streams API: filter, map, reduce, collect, etc. Lambda expressions and their use cases. Method references and functional interfaces. Optional class: usage to avoid null checks. Java Memory Management and Garbage Collection: How Java memory model works (Heap vs Stack). Garbage collection: What is it, different types (Minor GC, Major GC), and how JVM manages memory. Finalization and the finalize() method. Memory leaks: Common causes and how to prevent them. Concurrency and Multithreading: Thread creation (extends Thread vs implements Runnable). Synchronization and deadlock resolution. Executor framework (ExecutorService, ThreadPoolExecutor). CountDownLatch, CyclicBarrier, Semaphore: How they work and when to use them. Thread safety: Making your classes thread-safe using synchronization or other methods (like Atomic variables). Design Patterns: Singleton (thread-safe variants), Factory, Builder, Observer, Decorator, Strategy. Understand creational, structural, and behavioral patterns. Real-life scenarios where you’ve applied design patterns (you might get asked for this). Java I/O: Byte vs Character stream. BufferedReader, FileReader, FileWriter, PrintWriter. Serialization: What it is, how to implement it, and use cases. NIO (New I/O): Channels, Buffers, and non-blocking I/O (Optional but can be useful for a senior role). Java 8 Features (if you’re not already well-versed, this is crucial): Default methods in interfaces. Streams API (filter, map, reduce). Optional class. Date and Time API (java.time): LocalDate, LocalTime, LocalDateTime, Period, Duration. Java 9, 10, 11, and beyond (Optional but important for senior roles): Module system (Java 9): Modular applications. Var keyword in Java 10. New HTTP client API (Java 11). New features added in Java 12+, especially if the company is using a recent Java version. Frameworks & Libraries (Key for senior Java roles): Spring Framework: Spring Boot: Why use it, how it simplifies development. Spring Dependency Injection: Constructor-based vs Setter-based DI. Spring MVC: Controllers, RequestMapping, RESTful web services. Spring Security: Authentication, authorization, JWT tokens. Spring Data JPA: Repository pattern, Spring Data features. Spring AOP (Aspect-Oriented Programming): Cross-cutting concerns. Spring Boot Actuator: Health checks, metrics, application management. Hibernate/JPA: Entity mapping, One-to-Many, Many-to-One, Many-to-Many relationships. Lazy vs Eager fetching, FetchType, and performance considerations. HQL and Criteria API for querying. Transactions, Session management, and caching. RESTful APIs: Creating RESTful services using Spring Boot. HTTP methods (GET, POST, PUT, DELETE) and status codes. Content negotiation (JSON, XML). Swagger for API documentation. Handling request validation and error handling. Microservices: How to design microservices with Spring Boot and Spring Cloud. Service discovery (Eureka, Consul). Circuit breakers (Hystrix, Resilience4j). API Gateway (Zuul, Spring Cloud Gateway). Inter-service communication (REST, messaging queues like Kafka, RabbitMQ). Databases: SQL: Joins (INNER, LEFT, RIGHT, FULL), GROUP BY, HAVING, ORDER BY. Subqueries, Transactions, Indexes, and Normalization. SQL optimization and understanding EXPLAIN plans. Writing efficient queries and understanding their performance. NoSQL (Optional): Basics of NoSQL databases like MongoDB, Cassandra, and their use cases. Working with JSON in NoSQL systems. DevOps & Build Tools: Maven vs Gradle: Dependency management, build lifecycle, and tasks. Docker: Basics of containerization and how to run Java apps in Docker containers. CI/CD: Jenkins, GitLab CI, and how to automate build and deployment pipelines. Version control: Strong knowledge of Git (branches, merge conflicts, rebasing, cherry-pick). Testing: Unit Testing: JUnit 5: Writing unit tests with JUnit. Mockito: Mocking objects for unit testing. Test Driven Development (TDD): Writing tests before code. Integration Testing: Testing with Spring Boot (using @SpringBootTest, @MockBean). Database integration testing with H2 or TestContainers. System Design (Highly Important for Senior-Level Interviews): Design scalable and high-performance systems. Understand load balancing, caching, database sharding, API rate-limiting. High availability and fault tolerance strategies. Microservices architecture and designing systems that scale. Soft Skills and Behavioral Questions: Leadership: Experience leading teams, mentoring juniors, code reviews. Problem-solving: How you approach debugging, optimizing code, and handling unexpected issues. Collaboration: How you work with cross-functional teams (product, design, QA). Communication: Explaining complex technical topics clearly. Let me know in the comment, If you feel I have missed anything which is important. And All The Best for your next interview.

Tag: java

Topic You Must Revise Before Your Java Interview

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