Qiu Zhao wanted to go to JINGdong, met three times, but got unexpected joy and won the Offer of 20K.

preface

Today to share with you fresh water friends three jingdong to win the Offer of the interview process, 20K still feel cabbage price, dizzy!

One side (1 hour 30 minutes)

1. Class loading mechanism concept, loading steps, parent delegate mechanism, overall delegate mechanism, class loader type and inheritance relationship
2. How to implement the class loader to load resources on the network file? How do I customize class loaders? Do custom loaders still comply with parental delegation? How to break the parental delegation mechanism?
3. How many ways can you instantiate an object?
4. The clone method of Object class extends to the difference between deep and shallow replication
5. The concept, usage and practice of reflection
6. Java memory model and JVM memory structure
7. With a 4-core 8GB machine, how much memory should be allocated to the heap and vm stack in the JVM? (Initial value, maximum value, allocation ratio between young generation and old generation of heap, etc.)
8. What is the effect of allocating too little or too much memory to young generations in the heap? Does copying cause stop-the-world?
9. What parameters set memory allocation in the JVM?
10. Need to share a variable in the thread scope, how to achieve? ThreadLocal source code implementation, Key weak references caused by memory leaks, how to avoid?
11. The role of volatile, implementation mechanism, cache consistency implementation
12. AtomicInteger atomic class function, source code implementation mechanism
13. The CAS lock-free algorithm concept, the source code implementation mechanism, the Unsafe class source code extends to the corresponding C++ methods of the HotSpot virtual machine and then extends to the corresponding assembly functions
14. ReentrantLock non-fair lock source implementation, AQS source implementation, why need to spin lock? Lock expansion process?
15. Usage scenarios, common parameters, and rejection policies of thread pools
16. Types of blocking queues, underlying data structures, and usage scenarios
17. Handwriting BIO Socket programming, BIO and NIO differences
18. Netty thread model, zero copy, sticky package unpacking, heartbeat mechanism, Pipeline source code
19. Principles in chain of responsibility models, policy patterns, template patterns, and design patterns
20. Top K problem, find tens of millions of numbers from large to small in the Top 10 numbers
21. In MySQL, clustered indexes are different from sparse indexes, and more indexes are better. What fields are suitable for indexing?
22. Index coverage and back table concepts, how to avoid back table?
23. Why B+ trees and not AVL trees?
24. The underlying implementation of a transaction
25. The concept and implementation mechanism of MVCC
26. Why is Redis so fast? Why not multithreading?
27. Hash table query time complexity, hash conflict solution?
28. The application scenario of Sorted Set, the implementation of hop table, the time complexity of query and insert?
29. Dubbo application scenarios, underlying communication components, service degradation, load balancing, interface exposure, serialization methods, let you implement a simple RPC framework what would you do?
30. Zookeeper application scenario, Watch mechanism, leader election algorithm, ZK distributed lock
31. Symmetric encryption, asymmetric encryption, digital certificates, HTTPS connection process, SSL encryption is certain security? At what layer does SSL implement encryption?
32. OSI layer 7 protocol? On which floor does the router work? At what layer do HTTP, TCP, FTP, and DNS work?
33. The functions and flow of ARP
34. Git operation, code conflict resolution methods
35. Redis cache penetration, cache avalanche, data consistency solutions
36. Elasticsearch inverted index, index and document
37. RabbitMQ application scenarios, production/consumer and publish/subscribe concepts and applications, data loss issues
38. Overselling solutions, MySQL optimistic lock and Redis optimistic lock
39. SQL > select * from student whose course average is greater than 85;
40. Algorithms: write merge sort and fast sort, analyze the time complexity, how to evaluate whether a stable sorting algorithm?

Second interview (50 minutes)

HR surface (18 minutes)

1. What do you think of the difficulty of the written test?
2. I see your comprehensive scores in the first few rounds are quite high. Do you want to develop in Beijing in the future?
3. Like Guangzhou, Shenzhen, Hangzhou Internet companies are a lot, why the post in Beijing?
4. I may be blunt. Your education background is relatively low among the candidates. What do you think is your advantage?
5. Have you thought about going to graduate school? Do you think you have the ability to do these jobs in a few years?
6. Why do you think you didn’t go to some of the better schools? Do you choose your major?
7. How long is the internship? A comment on the first two rounds of interviewers?

conclusion