Pinduoduo failed miserably in three aspects. Java middleware, database and spring framework can’t answer

Time:2022-5-15

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Pinduoduo failed miserably on three sides. Java middleware, database and spring framework can’t answer

Interview open rocket, work screw At the beginning of this month, a friend had a lot of interviews. One side was full of confidence, but three sides failed miserably Yesterday, my friend asked me out to discuss the problem, but I couldn’t answer it on three sides (the jam is very serious). After listening to the whole interview experience, I summarized that this time I put more than one, two or three aspects. In fact, I asked five aspects, namely self introduction + project, Java foundation, middleware, database and spring framework, as well as an algorithm. Next, let’s take a look at pinduoduo’s experience and see if you can easily deal with the bombardment of the interviewer?

Pinduoduo failed miserably in three aspects. Java middleware, database and spring framework can't answer

Part I Project + self introduction

  • First, come up and briefly introduce yourself?

  • Then let’s introduce the project in the resume and talk about the difficulties and technical structure of the project.

  • What problems have you encountered in the process of development?

  • Usually communicate with colleagues like this?

The second part is the basic aspects of Java

  • The first is the old HashMap. What is the time complexity of HashMap’s set and get? Why o (1), HashMap in jdk1 Is 8 thread safe?

  • Why is it thread safe? Concurrenthashmap understand? How does he achieve thread safety?

  • Talk about Java generics. Why is java generics called pseudo generics? What are the benefits of generics? Can int be a generic type?

  • Say staticAnd dynamicWhat’s the difference? How is the bottom layer of dynamic * * * implemented?

  • What is the difference between thread run and start? What happens if you start the same thread twice?

  • Talk about the java thread model? Say the violate keyword? What is his principle? Is thread violet safe? Tell me the difference between violate and synchronized keywords?

  • How does the process pool work? Have you ever used thread pools in your project? How? What is the difference between core threads and non core threads? How do you determine the number of core threads in the project.

  • Do you know the concurrent package? What is CAS? How can CAS solve the ABA problem? Tell me the difference between countdownlatch and cyclicbarrier?

  • Talk about the working mechanism of Java class loader? Let’s talk about JVM. Have you made GC tuning? Tell me about it?

Part III spring framework

  • What is the difference between beanfactory and ApplicationContext?

  • How to configure spring based on XML configuration

  • Tell me about the startup process of springboot? What annotations are usually used in development?

  • How does spring quickly create product ready applications?

  • How to deploy to different servers using spring boot?

The fourth part is about database and Java middleware

  • What are the common data structures used by redis, which ones have been used in your project, and the scenarios used in business,? Has redis cluster learned how to achieve high availability?

  • What is the difference between redis cluster and sentinel mechanism? Do you understand the persistence mechanism of redis? How do you do persistence in the project? Have you met the hotkey of redis? How? Is redis single threaded? Why is single thread so fast? Redis implements distributed locks and compares the performance and stability with ZK?

  • Kafka principle? How to ensure that messages are not lost?

  • What are the common implementation methods of index and what are the differences? What are the storage engines of MySQL and what are the differences? How and how does InnoDB implement indexing? What’s the difference between clustered index and non clustered index?

  • A large number of messages are consumed per page. Can an oom exception occur?

  • What happens when you send a publish message to a nonexistent exchange? What happens when you perform a consume action on a nonexistent queue?

  • Why not use persistence mechanism for all messages?

The fifth part is about the algorithm (two questions in total)

  • The handwritten question is leetcode 106 The binary tree is constructed from the middle order and post order traversal sequence, and the binary tree is constructed according to the middle order traversal and post order traversal of a tree. (Note: you can assume that there are no duplicate elements in the tree.)

For example, given inorder = [9,3,15,20,7] and postorder = [9,15,7,20,3], the following binary tree is returned: 3 / \ 9,20 / \ 15,7

  • The handwritten question on both sides is leetcode 86 Separate linked list

Given a linked list and a specific value x, the linked list is separated so that all nodes less than x precede those greater than or equal to X. You should keep the initial relative position of each node in both partitions. Example: input: head = 1 – > 4 – > 3 – > 2 – > 5 – > 2, x = 3, output: 1 – > 2 – > 2 – > 4 – > 3 – > 5

The answer analysis of these two algorithm questions is in the document leetcode Chinese version. PDF

Pinduoduo failed miserably in three aspects. Java middleware, database and spring framework can't answer

Final summary

Generally speaking, I feel that my friend still doesn’t review enough, otherwise I won’t fail miserably in the interview. Moreover, most of the answers to these questionsIt’s all in the following file

Pinduoduo failed miserably in three aspects. Java middleware, database and spring framework can't answer
Pinduoduo failed miserably in three aspects. Java middleware, database and spring framework can't answer

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If you’re interested in this answer,If you need to refer to the original PDF to learn + brush questions, you can help support the third company