Comprehensive Collection of Major Tech Company Interview Questions (Java, Spring, MyBatis, Redis, Multithreading)

September marks the peak hiring season, and many fresh graduates and experienced professionals face intense competition and even contract breaches during job hunting.

To help candidates stand out, we have gathered interview questions from major tech firms collected in July and August, and compiled them into a free "Gold September, Silver October" interview question collection.

Java Basics Interview Questions

1. What are the characteristics of object‑oriented programming? 2. Differences among public, private, protected, and default access modifiers? 3. Is String a primitive data type? 4. Is the statement float f = 3.4; correct? 5. Does short s1 = 1; s1 = s1 + 1; cause an error? What about s1 += 1;? 6. Does Java have a goto keyword? 7. Difference between int and Integer? 8. Difference between & and &&? 9. Explain the usage of stack, heap, and method area in memory. 10. What are the results of Math.round(11.5) and Math.round(-11.5)? 11. Can switch be used with byte, long, and String? 12. Most efficient way to compute 2 × 8? 13. Does an array have a length() method? Does String have one? 14. How to break out of multiple nested loops in Java? 15. Can a constructor be overridden? 16. Is it possible for two equal objects to have different hash codes? 17. Can the String class be extended? 18. When an object is passed to a method and its fields are modified, is this pass‑by‑value or pass‑by‑reference? 19. Differences among String, StringBuilder, and StringBuffer. 20. Difference between overload and override; can overload be distinguished by return type?

Java Multithreading and Concurrency Interview Questions

1. Difference between daemon threads and user threads? 2. Difference between threads and processes? 3. What is a context switch in multithreading? 4. Difference between deadlock, livelock, and starvation? 5. Which thread scheduling algorithm does Java use? 6. What is a thread group and why is it discouraged? 7. Why use the Executor framework? 8. Difference between Executor and Executors? 9. What is an atomic operation and which atomic classes exist in the Java Concurrency API? 10. What is the Lock interface and its advantages over synchronized? 11. What is the Executors framework? 12. What is a blocking queue and its implementation principle? 13. How to use a blocking queue for a producer‑consumer model? 14. What are Callable and Future? 15. What is FutureTask and how to start a task with ExecutorService? 16. How are concurrent containers implemented? 17. How many ways exist for thread synchronization and mutual exclusion? 18. What is a race condition and how to detect/solve it? 19. How to use and analyze a thread dump? 20. Why does calling start() execute run() but calling run() directly does not start a new thread? 21. How to wake a blocked thread? 22. What is a re‑entrant lock? 23. What is the purpose of volatile and typical use cases?

Spring Framework Interview Questions

1. What is the Spring Framework? 2. List the advantages of Spring. 3. What functionalities does Spring provide? 4. How many modules does Spring have and what are they? 5. What is a Spring configuration file? 6. What components make up a Spring application? 7. What are the ways to use Spring? 8. What is the Spring IoC container? 9. What is dependency injection? 10. How many ways can dependency injection be performed? 11. Distinguish constructor injection from setter injection. 12. How many IoC containers exist in Spring? 13. Compare BeanFactory and ApplicationContext. 14. List some benefits of IoC. 15. How does Spring implement IoC? 16. What is a Spring bean? 17. What configuration methods does Spring provide? 18. Does Spring support bean scopes? 19. What is the lifecycle of a Spring bean? 20. What is an internal Spring bean? 21. What is Spring autowiring? 22. What are the autowiring modes? 23. Limitations of autowiring.

Redis Interview Questions

1. What is Redis? 2. Data types supported by Redis? 3. Benefits of using Redis? 4. Advantages of Redis over Memcached? 5. Differences between Memcached and Redis? 6. Is Redis single‑process single‑threaded? 7. Maximum size of a string value? 8. Persistence mechanisms and their trade‑offs? 9. Common performance problems and solutions? 10. Deletion strategy for expired keys? 11. Eviction policies? 12. Why does Redis keep all data in memory? 13. Synchronization mechanisms? 14. Benefits of pipelining? 15. Experience with Redis cluster and its principles? 16. Scenarios that can make a Redis cluster unavailable? 17. Java clients for Redis and recommended one? 18. Comparison of Jedis and Redisson? 19. How to set and verify a password? 20. Concept of hash slots? 21. Master‑slave replication model? 22. Possibility of write loss in a cluster and why? 23. How clusters replicate data? 24. Maximum number of nodes in a cluster? 25. Selecting a database in a cluster? 26. Testing Redis connectivity? 27. Understanding Redis transactions? 28. Transaction‑related commands? 29. Setting expiration vs permanent keys? 30. Memory optimization techniques? 31. How the Redis reclamation process works? 32. Ways to reduce memory usage? 33. What happens when memory is exhausted? 34. Multi‑threaded implementation in Redis?

MyBatis Interview Questions

1. What is MyBatis? 2. Advantages of MyBatis? 3. Disadvantages of MyBatis? 4. Suitable scenarios for MyBatis? 5. Differences between MyBatis and Hibernate? 6. Difference between #{} and ${} placeholders? 7. How to handle mismatched property and column names? 8. Writing fuzzy LIKE queries? 9. How does a DAO interface work with XML mappers? Can overloaded methods exist? 10. How does MyBatis implement pagination and the principle of pagination plugins? 11. How does MyBatis map SQL results to objects and what mapping forms exist? 12. Performing batch inserts? 13. Retrieving auto‑generated primary keys? 14. Passing multiple parameters to a mapper? 15. Purpose and implementation of dynamic SQL; types of dynamic SQL? 16. Additional tags in XML mapper files besides select, insert, update, delete? 17. Can id be duplicated across different XML mapper files? 18. Why is MyBatis considered a semi‑automatic ORM? 19. One‑to‑one and one‑to‑many association queries? 20. Ways to implement one‑to‑one relationships? 21. Ways to implement one‑to‑many relationships? 22. Does MyBatis support lazy loading and its mechanism? 23. First‑level and second‑level caches? 24. Different ways to write a mapper? 25. How MyBatis plugins work and how to write one.

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