Preface
I started to participate in the autumn recruitment at the end of September this year. I also took a lot of offers, and I finally chose to enter Jingdong! Many people ask me to send out the specific process, but I don’t think I’m lazy! But thinking that I can go ashore on JD.com, thanks to the previous interviews shared by big guys on the Internet, now I have come to learn how to write the big guys! I wrote it for the first time. Many summaries were not in place. I hope you don’t mind! On the whole, I still pay more attention to the basics, mainly Java and computing network! Then the items on the resume should be very familiar. On the second side, the interviewer will ask the items in detail. Finally, I have to boast. Jingdong’s entire interview process is still very fast, and the interviewers are very good. The interview experience well!
In addition, I am here to prepare interview materials for first-line manufacturers and my original super hard-core PDF technical documents, as well as a number of interview questions from large manufacturers that I have carefully prepared for you (constantly updated). Friends in need click here to remark csdn , Download it yourself ! Hope everyone can find the job they want!
one side
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Originally a video interview, but because the interviewer's video had some problems, it was changed to a telephone interview. The fruit phone cannot record the phone, so the question is missing. The whole journey takes 26 minutes, including Java data types
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What is value transfer in Java? What is reference transfer? The
basic type is value transfer, and the reference type is reference transfer. -
What data types are there?
I answered list, stack, queue, set -
What is the difference between ArrayList and LinkedList The
former array has low search time complexity and high delete time complexity, which requires expansion;
The latter linked list has high search time complexity and low deletion time complexity, and does not require expansion
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Do you know HashSet?
Know that the bottom layer actually encapsulates HashMap -
What is the difference between ArrayList and HashSet?
One is a list and the other is a set. The set guarantees the uniqueness of the data, while the list does not -
When to use Set and when to use list
? ? ? Use set when you need to ensure that the data is unique, and use a list when you don’t need it -
How to ensure the uniqueness of data?
Because its bottom layer is HashMap, we need to ensure that the result obtained by his hashcode() method is unique, so we can override this method. -
The difference between String, StringBuffer, StringBuilder
String: immutable, thread safe
StringBuffer: Variable, thread safe
StringBuilder: Variable, thread unsafe
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When to use the above three?
It depends -
What is Spring IoC?
Inversion of control, that is, creating a new bean instance does not need to use a class to perform new, but is achieved through construction methods, method settings, and dependency injection methods. -
What annotations have been used?
@Autowired is used for automatic loading, @Controller annotates Controller class, @Service annotates Service class, @Configuration annotates configuration class, etc. -
What is the difference between @Autowired and @Resource?
Don't know, never used the latter -
What should I do if @Autowired is written in the code but I actually don't want him to load it?
I answered that the package of this class is removed from the scanned package in the @ComponentScan annotation -
What are the advantages and disadvantages of Spring singleton?
Benefits: The life cycle of the bean is completely controlled by the container, and there is no need to worry about the creation of classes and the waste of space
Disadvantage: if there are some variables or something, it may cause thread insecurity
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Is there any way to solve the above thread safety problem?
You can directly add the synchronized keyword to the attribute, or make the attribute private and access it through methods. These methods must be modified with the lock or synchronized keyword. -
What if there is no lock?
Can use spin lock + CAS method -
What is the difference between # and $ in Mybatis?
do not know. . . -
What is Spring AOP?
Aspect-oriented programming -
What's the problem?
Slightly
Two sides
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emmm. . It was the phone call again, and there was no recording. The whole journey takes less than 30 minutes, and it feels okay
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Asked project-related questions
slightly -
JVM's garbage collection algorithm?
Mark delete, mark copy, mark sort -
The background and application of the red-black tree
(how do I know the background... Who proposed it for several years?) Applications such as HashMap in Java (try to talk about what you know) -
Does the operating system understand?
Except for some commands used daily, others are not very clear, such as kernel mode and user mode. -
What command is used to check whether the port is occupied? How to check the TCP connection of the port?
Use lsof -i for the former, and netstat for the latter. -
The distributed locks used in the
project are useless in the project, but you can use the database, redis, and zk for distributed locks -
Database transaction isolation level
four
Read uncommitted, read committed, repeatable read, serialization
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The lock
emmm in the database . . . If speaking from the scope of locks, there are table locks, page locks, row locks, and global locks. If you talk about the bottom layer, there are record lock, gap lock, and next-key lock. If there is a competition mechanism for locks, there are optimistic locks, pessimistic locks, and many -
What are the locks in common engines?
The above locks are available in innodb. But MyISAM does not support transactions, so it only has global locks. -
Some distributed transaction algorithms?
do not know. . . -
The main contribution in the project?
slightly -
Which ones have helped you the most in your academic career?
slightly -
What's the problem?
slightly
Three sides
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The difference between List and Set
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List commonly used implementation classes
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The difference between ArrayList and LinkedList
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Set commonly used implementation classes
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The difference between HashSet and LinkedHashSet
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The difference between int and Integer
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The difference between == and equals
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final keyword
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The difference between interface and abstract class
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Atomic operations, CAS problems, how to solve
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++ and-whether the operation is atomic and why
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Java's exception handling mechanism, the difference between Error and Exception
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Does IOException need to be caught?
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The difference between synchronized and Lock
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Thread pool: creation, core parameters, rejection strategy
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Spring dependency injection
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It does not matter whether there is a bean or not, what method should be injected
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Redis data types, commonly used Redis commands
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The difference between # and $ in MyBatis
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The leftmost matching principle of Mysql joint index
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Project-related, just let me talk about it, without in-depth questions
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Rhetorical link
HR face
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There is no recording on the phone, and the answer is not answered after the questions are listed, and it is useless to refer to it depending on the person. The interviewer felt that she was a newly recruited lady, and she didn't feel very energetic. . . Everyone must cheer!
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Asked about undergraduate schools and postgraduate entrance examinations
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See you have only one project experience, why?
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Asked about the college
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Are there any preparations for the internship? (I??? I can’t prepare for an internship?)
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What are the key elements when looking for a job?
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Have you voted for anything recently?
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You just mentioned the salary issue, what is your salary expectation?
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(Because of the offers on hand) Have some offers meet your expected salary?
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What do you think of xx company and JD?
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career planning
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How do you think about overtime?
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In career planning, what shortcomings will affect you?
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What your classmates and teachers say about you
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Own advantages
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What's your question?
to sum up
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