35 High-Frequency Java & Spring Boot Interview Questions (Quick Revision Cheat Sheet)

Hey developers! 👋

While prepping for Java Backend roles, I noticed how time-consuming it is to dig through lengthy documentation, verbose blogs, or multi-hour videos right before an interview.

To streamline last-minute revision, I put together a concise 35-Question Cheat Sheet covering core Java and Spring Boot internals.

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🔑 Core Topics Covered in the Cheat Sheet

1. Core Java & Collections Internals

• HashMap vs ConcurrentHashMap: Bucket structure, segment locking vs CAS, rehashing mechanics, and thread-safety trade-offs.
• String Pool & Immutability: Heap memory allocation, garbage collection behavior, and string literals vs new String().

2. Multithreading & Concurrency

• Concurrency Primitives: volatile keyword guarantees, visibility vs atomicity.
• Executors & Futures: ExecutorService thread-pool behavior, rejection policies, and CompletableFuture async pipelines.

3. Spring Boot & Microservices

• Spring Core Mechanics: @EnableAutoConfiguration under the hood, @Bean vs @Component.
• Error Handling & Fault Tolerance: Centralized @ControllerAdvice exception handling and Resilience4j Circuit Breaker state transitions.

4. Persistence & Database (JPA/Hibernate)

• Performance Tuning: Fixing N+1 select queries, proxy initialization, and fetch strategies (LAZY vs EAGER).

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📚 Get the Complete 35-Question Revision PDF Pack

If you want the full structured PDF with detailed questions and answers for quick revision:

👉 Download the Java & Spring Boot Interview Cheat Sheet (₹49)

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Hope this breakdown proves helpful in your technical interview prep! Feel free to share your thoughts or drop questions in the comments below.