It's awesome! Crazy brushing JD Java interview questions for three months, and finally got 35K13 salary in JD.

Preface

I have to talk about this from three months ago: At that time, a water friend told me that I wanted to move to JD.com , and then I supported it with the mentality of helping the fans and cheering up for the fans (or maybe watching the excitement be too big?) He must go, his dream must be there, maybe it will come true?

did not expect. . . . . . . Directly cool!

 

The following is the first Jingdong Ermian Liangjing

Jingdong side cool scripture

1. Object method, 7 methods
2. Synchronized method explanation
3. The realization principle of synchronized method
4. The principle of the volatile keyword
5. Classification of locks
6. Deflection lock explanation
7. The difference between NoClassDefFoundError and ClassNotFoundException
8. Ask me whether ClassNotFoundException only occurs at compile time, and can it be done at runtime
9. Class loading mechanism
10. Redis expiration strategy and memory elimination mechanism
11. 4 types of mysql indexes
12. The difference between Innodb and myIsam
13. Innodb index structure
14. Advantages and disadvantages of B+ tree
15. What is the impact of the index of massive data
16. Choose joint index or multiple index, the rule of the leftmost prefix
17. CAP theory relationship
18. Which systems have you seen, guarantee two sacrifices one
19. Consistency Hash

算法题：
给一个正数N，求这个N的所有的因子分解；
N = 12；
Ans = {12},{6,2},{3,4},{3,2,2}
解法：递归
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Jingdong Ermian Liangjing

1. Self introduction + project
2. How is asynchrony in the project done? Specifically
3. How to ensure the security of user passwords?
4. How to achieve the bottom of mybatis? (will not)
5. What is the difference between congestion control and flow control in tcp?
6. How exactly is flow control controlled?
7. What is the specific algorithm for congestion control?
8. What is the use of locks in Java?
9. Talk about the difference between syn, re and cas?
10. How realistic is cas?
11. The difference between process and thread? Specifically, under what circumstances is multi-process and under what circumstances is multi-threaded?
12. What are the maps in java? Each brief introduction
13. What is the underlying data structure of hashmap?
14. Is there a map sorted by key value? How realistic is the bottom layer?
15. The loading process of the class? What exactly did each step do?
16. The scope of Spring Bean.

两道算法题
1、有序二维数组找target，找到返回坐标，找不到返回[-1, -1]；
2、树的根节点到叶子节点的所有路径和。
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Failure is the mother of success

The above is the whole content of the first JD interview. One side and two sides are followed. It lasts for 2 hours. After experiencing it, I have one feeling: JD’s interview is too hard-core , but I will always ask the end and see if you master it. To what extent, it is easy to be asked if you do not master it deeply. Let the fans go home after the two sides, and PASS is also very subtle.

But do you think this is over? of course not!

As far as I know, JD.com has a three-month lock-in time for delivery of resumes, so failure this time does not mean there will be no next time.
Then I summarized the experience and prepared for the next interview and started a three-month retreat.

1. Make up for the underlying knowledge of JAVA concurrency, especially synchronized, volatile and hashmap
2. Brush algorithm questions, you need to review the knowledge of data structures and algorithms in detail
3. Understand the problem solutions and performance tuning under high concurrency
4. Reading is the source code of the spring framework to enhance your competitive advantage

Regroup and fight JD

This time the interviewer really came up and asked directly: Seeing that you also came to JD.com in June but failed, what do you think is your current advantage? ?

Answer: Because I was not fully prepared for the interview at your company last time, and at the same time, I realized that I did not have enough technical aspects, so I went back and studied systematically. I think I can do the job this time!

Then the interviewer looked at him and smiled (it should mean appreciation), and then the second interview officially began!
Because the second interview is not much different from the first one, the content of the second interview is shared with everyone through the classification of knowledge points.

JVM

1. What kind of garbage is recycled?
2. How to use JFR and JMC to monitor Java programs?
3. Explain the Java virtual machine memory model
4. JVM garbage collection mechanism
5. What kind of objects will enter the old age
6. Talk about OOM and tuning

MySQL

1. Tell me about my understanding of the two common storage engines of MySQL: MyISAM and InnoDB?
2. Do you understand database indexes?
3. Why can index improve query speed?
4. How does Mysql add indexes to table fields?
5. What are the common optimization methods for large tables?

spring

Maybe it is written on the resume that I have read the source code, so I asked spring more this time

1. What design patterns are used in the Spring framework?
2. The realization method and principle of Spring transaction
3. What is the difference between Bean Factory and ApplicationContext?
4. What is dependency injection in Spring?
5. What are the different types of IOC (dependency injection)?
6. Explain the life cycle of Spring Bean?
7. What are the important bean life cycle methods? Can you rewrite them?

distributed

1. Why use redis cache?
2. Why use redis instead of map/guava for caching?
3. What is the difference between redis and memcached?
4. Redis common data structure and usage scenario analysis? (String, Hash, List, Set, Sorted Set)
5. redis sets the expiration time.
6. Redis memory elimination mechanism (There are 2000w data in MySQL and only 20w data in Redis. How to ensure that the data in Redis is hot data?)
7. Redis persistence mechanism (how to ensure that the data can be recovered after redis hangs and restarts)?
8. redis affairs.
9. Solutions to cache avalanches and cache penetration problems.
10. How to solve the key problem of concurrent competition in Redis.
11. How to ensure data consistency between the cache and the database when it is double-written?
12. What is a message queue? Why use message queues?

Summary of the second interview

The second time I went to Jingdong for an interview because it took a long time to prepare, so the interview questions were basically expected. In the end, I successfully won the offer from Jingdong. Congratulations!

Finally , I will share the information about the success of the interview with Jingdong for free, and I wish everyone a promotion and salary increase!
Some readers commented in the message area that I am selling materials. Please rest assured that the following materials will never charge you any fees. Private Message Editor [Notes] or directly add WeChat mxj94670  to get this information.

 

 

I heard that all the fans of the one-click three consecutive interviews succeeded? If this blog is helpful to you, please support the blogger

Friends who need the above interview questions, privately message my keyword "notes" after three consecutive sessions or directly add the assistant WeChat mxj94670 to get it for free