Java Backend Interview Questions and Analysis

The article begins with a brief invitation to follow the public account "Java后端技术全栈" and encourages readers to reply "000" to receive a programmer's e‑book, then presents a list of typical interview questions encountered in a Meituan‑Dianping first‑round interview.

Questions include self‑introduction, memory‑leak experience, Java primitive types and why String is final, the underlying implementation of reflection and dynamic features, and detailed inquiries about HashMap (its structure, thread‑safety, put process, version differences) and ConcurrentHashMap (design, CAS usage, ABA problem and its solution).

The guide then examines the JVM thread model and runtime data areas (stack, heap, method area), emphasizing the distinction between Java memory model and JVM memory model, and discusses class‑loader mechanisms, the role of .class files, and object lifecycle.

Further topics cover Java's thread model, the semantics of volatile, read‑write locks, and other concurrency controls, followed by database indexing concepts (B+‑tree, composite vs. single indexes), MVCC mechanisms in MySQL, and strategies for optimizing slow queries.

Additional sections address using Redis to implement distributed locks (including setnx, Lua scripts, and cluster considerations) and Spring bean scopes, Spring MVC controller thread safety, and best practices for ensuring concurrency correctness.

The article concludes with a summary stating that about 90% of the listed questions can be answered by memorizing interview material, especially for engineers with less than five years of experience, and provides links to further reading on Redis cache design, design principles for architects, and Spring Boot integration with Kafka.