2018 Java Backend Interview Experience

       The landlord graduated in 2016 and entered the previous company in March 2016 until the end of March this year, so this is a two-year work experience to share.

       It is said that gold is three and silver is four. In the past few years, I have heard nothing special. This year, I really experienced a silver 4, and I got two offers from March 26 to April 17. The emotional fluctuations in it are amazing now that I think about it. Some are calm, some are irritable, some are flustered, some are fearful, some are devoted (swipe the interview questions, read the information), and finally add the joy of jumping up from the offer from the interview company that you like. (Here is a little experience: if you can, don't choose naked speech. Anyway, the landlord thinks so, judge on your own...)

       Let's start my journey of face-to-face scriptures, I hope it can help you reading. (The following interview questions are only for the part that the landlord remembers, please bear with me)

        1. Zhejiang Dahua Technology Co., Ltd.

       >>> This is a special scene, um... and then it hangs badly. The interviewer's first sentence: Introduce yourself, (balabala), and then glance at your resume. You have two years of work experience. I don't have much to ask. Not interested. Later I learned that the minimum requirement is 3). The last minute to hang up, the data structure and algorithm must be firm, not easy.

1. Quickly arrange to know, write; um, bubbling, know, write
2. Talk about a balanced binary tree
3. 3/4 Please keep two digits of precision, how to do it in java
4. Talk about depth first, breadth first
5. How to remove duplicate elements in hashmap
6. April 1, 2018 is the day of the week how to achieve

        2. Chinasoft Information System Engineering Co., Ltd.

        >>> When I talked to the technical director on the second side, I said that the current position is a maintenance-oriented position, so I went to the Huawei R&D center for a round of interviews (two rounds of technical interview + technical supervisor interview + Huawei technical interview + HR face), as long as the book is read and understood, there is basically no problem (in the final analysis, the foundation is still very important). The owner finally got the offer

1. Talk about the commonly used hibernate annotation methods
2. What are the annotation methods of springMVC's controller
3. How does java implement calling Web Service interface
4. Let’s talk about restful. For the request parameters, let’s talk about the annotations
5. If the request parameter of rest is an object, how to do it
6. Let's talk about java concurrency
7. Tell me about your best project
8. The benefits of using springMVC
9. talk about business
10. If you want to implement the server to push messages to the client, what will you do and what method will you use?
11. How StringBuffer is thread-safe
12. Reverse array elements, how would you implement
13. How to do relational mapping in hibernate
14. Why to override equals() method and hashCode() method
15. Have you understood the intermediate process of the client initiates a request to the server?
16. Do you know HashMap, talk about it
17. What is a memory leak
18. Handwritten quicksort, talk about code ideas
19. Talk about the memory division of jvm
20. Talk about the processing flow of springMVC

       3. Shanghai Dianrong Information Technology Co., Ltd.

       >>> Dianrong.com's java multi-threading question is relatively deep (experienced three rounds of technical + two HR rounds), although I successfully won the offer, but at the same time I found that some of my own infrastructure is not enough, I need to do A research and development should not only stop at how to use it, but should go deep into the bottom and stay away. Learning is like rowing against the current, if you don't advance, you will retreat! Let's share.

1. How to implement multiple threads to print the result after the thread execution ends
2. What is the final result of volatile modification of race resources?
3. I have a student object (student number, name), how to use Set to keep one of them
4. How does the bottom layer of HashSet implement deduplication?
5. How custom annotations are used (you define a custom annotation, how do you use it, and why do you use it)
6. How is the bottom layer of Executors implemented?
7. Why do you use ThreadPoolExcuter instead of ExecutorService and what are the uses of ExecutorService
8. Fair lock, unfair lock concept
9. How are unfair locks used and why are resources preempted?
10. Does ThreadLocal know? If I have a thread that maintains a variable with ThreadLocal, and this thread has many sub-threads, can I access the variable maintained by the main thread and why?
11. You used the observer pattern, so talk about it
12. What other design patterns do you know?
13. Do you know what a memory leak is?
14. When is garbage collection triggered and what is the trigger point?
15. Which objects are recycled
16. what is a large object
17. Let's talk about HashMap. I have two duplicate keys inserted into HashMap. How is the internal implementation implemented? Why rewrite the equals and hashCode methods
18. Let's talk about multi-threading, how to use it, what is the difference between Callable and Runnable
19. How is the JVM divided?
20. Where is the new object stored?
21. Which classes under the atomic package have been used and how are they used?
22. Let’s talk about restful, what requests does restful have, and what protocol does restful use
23. What do you think is the biggest difference between restful and webServie?
24. Based on your project, how do you understand business modeling Can you describe the whole process? How do you feel about business modeling?
25. To create a new instance, the new instance can be used through the session sharing technology; what other technologies can achieve this function (this question is roughly remembered, it should be other technologies that can replace session sharing)
26. do you know spring
27. Talk about countDownLatch
28. what is thread safety
29. Do you know the Java memory model?
30. Do you know the database three paradigms? If you can't remember, you don't need to explain the definition, just say it in your own words.
31. What is serialization and deserialization
32. Do you know proxy mode? What proxy mode does AOP use?
33. How is the bottom layer of JDK dynamic proxy implemented?
34. You have used git, tell me some git commands
35. Talk about java concurrency
36. Familiar with springboot? Did you know about spring cloud?
37. Which databases have you used? Have you ever used nosql database?
38. Have you used mongoDB?
39. How do I get the result returned after one or more threads execute

       4. Chengdu Wesige Technology Co., Ltd.

       >>> Wesige should be a traditional company, and the technical aspects are generally good, but the HR chat was not very happy (only two rounds), and in the end it was windy... People respect it, I respect it; People humiliate it, Yu Yuanzhi, encourage it...

1. How Java thread pool waits for some threads to end
2. Advantages and disadvantages of indexes
3. Talk about the double check (DCL) of the singleton pattern
4. How HashMap achieves thread safety
5. Difference between ArrayList and Linked
6. Tell us about a project you have been most involved in
7. know which locks
8. How the thread pool is used
9. What technologies have you used in your previous projects?

        5. Shenzhen Huize Insurance Brokers Co., Ltd.

        >>> To do the written test questions, it may be due to the new base of Huize.com this year, and the written test questions are relatively basic. But for a person with two years of work experience, I think the written test questions are very difficult. Anyway, the basics are important. Next, I will think about it carefully, and then list the test sites for the written test (headache...>_<), after a round of technical + CTO, and finally successfully won the offer. Basic, basic, basic, important things are said three times!

1. Part of the test site for the written test: Java class loading order; thread safety; Java basic type forced conversion; database query; packaging and unboxing of wrappers;
2. 数据库left join、right join、inner join、full join
3. The difference between HashMap and HashTable
4. HashMap principle, how to achieve its thread safety
5. Similarities and differences between Callable and Runnable to achieve multi-threading
6. HashMap multithreading causes problems
7. Why should HashMap use red-black tree implementation (benefits and losses)
8. Talk about a project you've done
9. Talk about the adapter pattern
10. Talk about Java IO programming
11. The program is prone to OutOfMemery problems, how did you troubleshoot
12. communication between processes
13. Involves multiple tables with complex business logic and writes specific sql statements
14. Tell me about the source code of what you've seen
15. What books have you read and what books are you currently reading?

       Summary : I hate less when the book is in use. Usually infrastructure is very important, important, and important! Together, I wish you and I progress together!