After Java interviews on JD.com, I found that it’s not that difficult to master these technologies

Preface

As a small editor who is obsessed with sharing technology , finally a group of friends fought against JD.com and successfully won an offer. Next, I will share with you the experience of interviewing on the five sides of JD. I hope that everyone can stand on the shoulders of giants and take a step forward , If the article is helpful to you, please pay more attention to support

JD Java side

1. Detailed description of HashMap, HashTable and CocurrentHashMap
2. Network IO model? What is multiplexed IO? The difference between select and epoll?
3. The TCP three-way handshake process, what is the problem if there is no third handshake?
4. What are the commonly used thread pools? Their respective application scenarios?
5. Java class loading mechanism? What are the benefits of the parental delegation model?
6. How much do you know about JAVA concurrent package components?
7. When does a deadlock occur in multiple threads? How to prevent it
8. Operating system's user mode and core mode switching conditions and why to switch
9. Characteristics of database transactions? Transaction isolation level? Transaction realization in the project? Examples of dirty reading, non-repeatable reading, and phantom reading?

JD Java two sides

1. Database index? B+ tree? Why build an index? What kind of fields need to be indexed, and what are the general considerations when indexing? Will the index reduce the efficiency of insert and delete operations, and how to solve it (sub-table operation)?
2. Design pattern, singleton pattern, how to ensure thread safety? The lock efficiency is too low, how to improve the efficiency?
3. CAS? What is the essence of CAS? What is atomicity? Compare and Swap two-step operation, why can guarantee atomicity (involving CPU instructions)?
4. What do you know about the implementation of distributed locks? Which lock do you recommend?
5. What are the persistence operations of Redis?
6. How to use redis to process hot data

JD Java Three Sides

1. Which message queue middleware have you contacted? How to choose?
2. Talk about your understanding of SOA and microservices?
3. Talk specifically about Spring Cloud service and registration?
4. Do you understand distributed caps and what do they mean?
5. Network programming nio is related to netty, netty's threading model, zero copy implementation?

JD Java Four Sides

1. Is Redis single-threaded or multi-threaded? How to do Redis distributed cluster?
2. Do you know about cluster avalanches?
3. Talk about the realization of peak shaving and current limiting in high concurrency scenarios?
4. What is personally the most satisfying among the projects you worked on before, talk about your architectural design ideas?
5. What are your plans for the next 2 years?

JD Java Five Faces (HR)

1. Why resign from the last company?
2. Why choose here?
3. How to treat overtime issues?
4. How do you usually learn technology, besides Java-related, what other technologies will you learn about?
5. What is the expected salary?

to sum up

The above is the whole process of Jingdong interview. If you want to go to a big factory for an interview, Java concurrency, performance tuning, and problem solving in high concurrency scenarios are the key. The next step is to summarize the interview questions. It is these interview questions that help the group of friends successfully win the offer!

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