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java-backend-interview-questions

Organizes Java backend interview topics and coding best practices into a searchable reference.

Updated Dec 23, 2025
Search Tags:#backend#java#Spring#design-patterns#interview-prep#MyBatis#JVM
One-click install
npx skills add https://github.com/BNTang/Sa-Token-Demo --skill java-backend-interview-questions
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: java-backend-interview-questions
Source: https://github.com/BNTang/Sa-Token-Demo/tree/main/.claude/skills/java-backend-interview-questions
Command: npx skills add https://github.com/BNTang/Sa-Token-Demo --skill java-backend-interview-questions

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

This Skill compiles and structures Java backend interview topics and coding best practices to help professionals study efficiently and answer questions confidently.

Core Features & Use Cases

  • Comprehensive topic coverage: Java fundamentals (serialization, exceptions, polymorphism, parameter passing, overloading vs overriding, inner classes), interfaces vs abstract classes, wrapper types, String handling, Java 8+/11+/17+/21+/25 features, JDK vs JRE, JDK tools, hashCode/equals, dynamic proxies, JDK proxies vs CGLIB, annotations, reflection, immutability, SPI, generics, deep vs shallow copy, class loading, parent delegation model, BigDecimal precision, new String object creation, final/finally/finalize, encoding issues, ProcessBuilder, thread start pitfalls, Stack vs Queue, Optional, I/O, networking, primitive types, autoboxing/unboxing, Iterator, runtime vs compile-time exceptions, inheritance, encapsulation, access modifiers, static vs instance, for vs foreach, wait vs sleep, Java vs Go, Object methods, bytecode, BIO/NIO/AIO, Channel, Selector, Float comparisons, POJO/VO/DTO/DAO/BO, data structures and collections, HashMap internals/performance, Hash collisions, ArrayList/LinkedList differences, expansion, HashSet vs HashMap, HashMap vs Hashtable, ConcurrentHashMap vs Hashtable, CopyOnWriteArrayList, List implementations, arrays vs linked lists, load factor 0.75, powers of two, network protocols (TCP/IP, OSI, HTTP versions, HTTP vs HTTPS, HTTP vs RPC, TCP vs UDP, stickiness/packet framing), Spring (IOC, AOP, circular dependencies, three-level cache reasons, beans lifecycle, MVC principles, DI), MyBatis, MySQL indexes and non-indexed scenarios, Redis data structures and strategies, Java concurrency (thread pools, locks, synchronization, NIO/Netty performance, concurrency utilities, volatile, thread life cycle, ABA), messaging queues, microservices, databases, design patterns (singleton), system design (seckill, short URLs, distributed IDs, RPC design), JVM, troubleshooting, CPU profiling, and more.
  • Practical guidance: Provides coding best practices, patterns, and troubleshooting tips with references to targeted material for deep dives.
  • Use-case oriented: Suitable for interview prep, onboarding, and as a fast-reference during technical interviews or code reviews.

Quick Start

Use this Skill as a study framework: skim the high-level topics, then dive into the linked references for thorough understanding and hands-on examples.

Frequently Asked Questions about java-backend-interview-questions

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How should I prepare for a Java backend interview covering Spring and JVM fundamentals?▼

Java backend interview preparation requires reviewing Java fundamentals, Spring framework concepts, JVM internals, and concurrency mechanisms. Structured repositories provide targeted guidance on bytecode, thread pools, and bean lifecycles to build comprehensive technical knowledge for technical interviews.

What is the difference between JDK dynamic proxies and CGLIB in Spring AOP?▼

JDK dynamic proxies and CGLIB differ in Spring AOP implementation. JDK proxies require interface implementation, while CGLIB creates subclasses at runtime. The Skill repository covers these differences alongside proxy mechanisms, reflection, and annotation processing for framework-level interview questions.

How does HashMap handle hash collisions and why is the load factor 0.75?▼

HashMap handles hash collisions using linked lists or tree structures when thresholds are exceeded. The load factor 0.75 balances time and space costs during rehashing. Study materials detail these internals alongside ConcurrentHashMap differences and capacity expansion strategies.

How do I resolve circular dependencies in Spring using the three-level cache?▼

Resolving circular dependencies in Spring involves the three-level cache mechanism, which stores early bean references to handle singleton injection cycles. The repository explains the cache reasons, bean lifecycle phases, and DI principles to clarify framework initialization behavior.

What are the best practices for Java concurrency thread pools and locking mechanisms?▼

Java concurrency best practices involve configuring thread pools appropriately, choosing between synchronization locks, and understanding volatile visibility. The Skill provides guidance on thread life cycles, ABA problems, and concurrency utilities to ensure safe multithreaded application design.

When should I use BIO, NIO, or AIO for Java networking and I/O operations?▼

Choosing between BIO, NIO, and AIO depends on concurrency requirements and I/O blocking behavior. BIO uses blocking streams, NIO employs Channel and Selector multiplexing, and AIO handles asynchronous callbacks. The repository details these models for performance and networking interview topics.

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