Summary of the Autumn Recruitment of 2021, Byte, Pinduoduo, Baixingwang (I have already got the offer)

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Position: Java back-end development

Interview record: Bytedance is kneeling on both sides, Pinduoduo is kneeling on the other side, and Baixingwang is accepting offers on three sides, and it is still in progress. . .

background

I am a master of 211 in the magic capital. Both graduate and undergraduates are mechanical (old robots). I have no choice but to hear that the mechanical profession is indeed not good, and the physical industry has collapsed.
So I got the idea of switching to a computer. During the period, I encountered a lot of setbacks. On the one hand, it came from the pressure of the teacher, and the other was really isolated at the beginning of self-study.
I have a clue, I don’t know what to learn [very broken], but I insist on persisting. In the process of constant frustration, I will become more and more sensitive to this language.

byte

one side

Self-introduction [In addition to introducing basic personal information, it is best to talk about your technology stack and project information]

What is a JVM memory barrier? What is the role? The principle of volatile?

What are the common garbage collectors and what are their characteristics? STW? Safe point? Jvm heap memory model?

Synchronized lock upgrade? principle? Deadlock concept? What effect does it have on static methods?

Does CAS understand? What's the problem? How to deal with it?

Principles of mysql index optimization? How to optimize sql? What is the underlying structure of the index?

TCP three-way handshake and four waved hands? Sticking and unpacking?

Three problems with redis caching? How to solve the cache breakdown? Redis implements distributed locks?

What are the intermediate technologies? Which rabbitMq application scenarios and implementation principles?

Common linux instructions? Count the number of characters?

KMP algorithm? Fast queue? (Tear the fast queue by hand, but the KMP is stuck in half)

Some questions about the project, such as table relationships, concurrent processing, the use of redis cache, the implementation of login functions, etc.

One side asks the special basis, the answer is okay, there should be two sides

Two sides

Self introduction

JVM tuning parameters? young GC and full GC? Generational age? CMS?

The underlying implementation principle of HashMap? [The difference between 1.7 and 1.8, expansion mechanism, hash collision, timing of linking list to red-black tree, why use red-black tree, etc.]

rentrantlock? How does AQS work? Fair lock and unfair lock? Deadlock?

Java object memory layout? Which attribute is the locked object related to?

mysql lock mechanism? The difference between read-write locks? Slow query log? Master-slave replication? The characteristics of innodb, compared with memory?

Redis cache and database consistency? The epoll principle of redis?

Design Patterns? DCL?

Dynamic programming [no]? Minimum spanning tree [nor will it]? ACM automata [nor will it]?

The two-sided algorithm didn't answer one of them, there was no idea, game over

Pinduoduo

The interviewer heard that I was a non-subject, and suddenly lost interest in me, hahaha

one side

Self introduction

Jvm heap memory model? Memory barrier?

The difference and principle of blocking IO and non-blocking IO?

The principle of HashMap and other layers? Expansion mechanism? Hash collision?

How does CAS work? Existing problems and solutions? Synchronized lock upgrade and principle? The principle of bias lock?

Optimistic lock and pessimistic lock? Application and principle?

Principles of mysql index optimization? How to do sql tuning?

DCL？

Common linux instructions?

Cardinality sort? LRU? The linked list is reversed?

The performance is average, but the interviewer thinks I am a non-major class, and I don’t want it very much.

People's Network

one side

Introduce yourself (ahhhhhhhhh)

The underlying implementation principle of HashMap? [From 1.7 linked list plus array to 1.8 linked list plus array plus red-black tree, hash conflict, expansion timing, linked list turning red-black tree timing, why red-black tree is better than B+ tree]

What are the garbage collectors? Which are the new generation and which are the old generation? The characteristics of CMS? What is STW? Safe point? Garbage collection process? Jvm tuning parameters?

What is a memory barrier? Why should volatile be added to DCL?

Heap memory model? What's the ratio? How to deal with memory allocation?

What are the characteristics of the storage engine used by mysql? What is the difference with memory?

How does redis implement distributed locks? Three problems? Data consistency?

What are the middleware technologies? Nginx reverse proxy and forward proxy?

The principle of synchronized lock upgrade?

The life cycle of spring bean object? The role of beanProcessor?

How does hystrix realize current limiting and fusing?

Two sides

Self introduction

Jvm class loading process? What is parental delegation?

Producer, consumer design pattern to write a case on-site?

How does volatile achieve memory visibility?

The difference between mysql read-write lock? Application scenario selection? Slow query log analysis?

Index optimization? mysql slow query log?

What problem does Bloom filter solve, and its realization principle? How to record the monthly activity of an app with redis?

The realization principle of spring aop and ioc? What is the difference between springboot and spring?

TCP sticking and unpacking? Three handshake and four waves?

What is asynchronous? The realization principle and usage scenarios of rabbitMq?

What problem does CAS solve? What's wrong with it? How to deal with it? What is the difference with synchronized?

Problems in the project: table structure, which fields are indexed, how tables are related, order processing business sequence diagram, sequence diagram of verification code login function, etc.

Three sides (hr side)

I talked about my personal situation, whether I would like to get a regular internship, I can come a few days a week, salary, took me to meet the department leader, very sincere, a nice interview, the most important thing is to regain my confidence.

to sum up

At the end of the article, the author has compiled a lot of information for everyone! Including a summary of the Java interview questions of the first-line manufacturers + the learning and thinking guide of each knowledge point + a summary of the Java core knowledge points of a 300-page pdf document!
Friends in need please also move to the official account: bright future, take it yourself! ! !