Ant Financial + Pinduoduo + Douyin + Tmall (technical three sides) face economic collection to help you get a big factory offer

Preface

Many Java developers may not have long working hours or rich work experience before the interview, so I don’t know what questions Internet companies or first-line Internet companies will ask in technical interviews? In addition, I may not have prepared enough. I was overwhelmed by a few questions by the interviewer within a few rounds of the interview, and ended up in a disastrous defeat. For these readers and friends, the editor has compiled some of the interviews of well-known big companies, and shared them here for readers and friends for reference, so that readers who are about to interview or have ideas to change jobs will understand those who like to ask during interviews with first-line big companies. problem.

Start

Ant Financial (three sides) Zookeeper + microservices + message middleware + high concurrency architecture design

one side

1. JVM data storage model, the structure of the new and old generations?
2. When does the java GC algorithm trigger minor gc and when does full gc trigger?
3. Which of the GC reachability analysis is considered GC ROOT?
4. JVM tuning parameters you are familiar with, and which tuning tools have you used?
5. What types of locks does Java have?
6. Describe the processing flow of the thread pool?
7. Class loading mechanism. There are several steps for loading a class into the virtual machine. Which of these steps are fixed in order, which is not fixed, why not
8. Hashmap is not thread-safe, and concurrenthashmap is thread-safe. How to achieve thread-safety?
9. What problem does the volatile keyword solve and what is the implementation principle?
10. What are the concurrent containers and the difference between concurrent and synchronous containers

Two sides

1. At work, SQL statement optimization and matters needing attention
2. Which libraries or frameworks use NIO
3. What kinds of injection methods are there in Spring, which ones to use under what circumstances, and the principle of ioc implementation
4. How to locate a slow query, how do you quickly locate a service with multiple SQLs
5. Do you know clustered index and non-clustered index? When to use a clustered index and what to use a non-clustered index
6. What storage structure does the Nosql engine use, what are the advantages and disadvantages of relational databases and NoSQL, and how to select the technology?
7. Under the microservice architecture, if there is an order system and an inventory system, how to guarantee transactions?
8. Distributed consensus protocol raft, do you understand paxos
9. ZAB protocol in Zookeeper, main selection algorithm

Three sides

1. Self introduction
2. Participate in concurrent projects, from design to deployment, follow the process to repeat.
3. Have you used redis for project-related purposes. In what scenarios and how did you use it?
4. The principle of mysql synchronization mechanism, what are the synchronization methods
5. How to realize database master-slave synchronization and how to realize transactions
6. Talk about your understanding of SOA and microservices, and the adjustments and challenges involved in distributed architecture from the application level.
7. What are the similarities and differences between Ali-based middleware metaQ and its principles and existing Kafka
8. Do you know any middleware in Ali? Implementation principle? What are the characteristics of other open source message queues?
9. Why choose to change company?
10. Career planning for three to five years?
11. Do you want to ask me?

Pinduoduo (three sides) phantom reading + segment lock + Spring Cloud + spike

one side

1. Brief introduction
2. ACID of the transaction, which explains the isolation of the transaction in detail
3. Dirty reading, phantom reading, non-repeatable reading
4. Red-black tree, binary tree algorithm
5. Which collections are commonly used? What is the difference between ArrayList and LinkedList? The internal data structure of HashMap? ConcurrentHashMap segment lock?
6. What optimizations have been made to hashMap and concurrentHashMap in jdk1.8
7. How to resolve the hash conflict, and if there is a conflict, how to find the target value in the hash table
8. The difference between synchronized and ReentranLock?
9. ThreadLocal? Application scenario?
10. Java GC mechanism? What are the GC Roots?
11. Will there be deadlocks in MySQL row locks?

Two sides

1. Do you understand optimistic locking and pessimistic locking? What is involved in optimistic locking and pessimistic locking in JDK?
2. Nginx load balancing strategy?
3. Have you compared Nginx with other load balancing frameworks?
4. Is Redis single threaded?
5. The reason for the high concurrency of Redis?
6. How to use Redis to process hot data
7. Talk about Redis sentinel, replication, cluster
8. What technology has been optimized at work? Talk about JVM, MySQL, code, etc.

Three sides

1. What does Spring Cloud use? How to achieve load balancing? How to judge if the service is down?
2. Network programming nio and netty related, netty thread model, zero copy implementation
3. What do you know about the implementation of distributed locks? Talk about an implementation method in detail
4. In high-concurrency application scenarios, what does the technology need to involve? How to design the architecture?
5. Next to the issue of high concurrency, it talked about the technical applications of spikes: kafka, redis, mycat, etc.
6. Finally, talk about the projects you have participated in, those with relatively high technical content, related architecture design and what core coding you are responsible for

Douyin

One side (50 minutes)

1. Hashmap, how to expand, how to deal with data conflicts? How to efficiently implement data migration?
2. How to realize Linux shared memory, probably talk about it.
3. Socket network programming, talk about TCP's three-way handshake and four waved hands
4. What is the difference between synchronous IO and asynchronous IO?
5. Java GC mechanism? What are the GC Roots?
6. Let’s talk about the red-black tree. Five features, insertion and deletion operations, time complexity?
7. The time complexity of fast sorting, the worst case, the best case, the time complexity of heap sorting, and the complexity of building a heap

Two sides (40 minutes)

1. Introduce yourself, mainly talk about what you have done and what you are good at
2. What do you know about design patterns?
3. How does AtomicInteger realize atomic modification?
4. What is the difference between ConcurrentHashMap in Java7 and Java8? Why is Java 8 concurrency more efficient? When to use HashMap and when to use ConcurrentHashMap?
5. Redis data structure?
6. Redis data elimination mechanism?

Three sides (about 1 hour)

1. The principle of mysql to achieve transaction (MVCC)
2. How is MySQL data master-slave synchronization achieved?
3. The realization of MySQL index, innodb index, how to implement b+ tree index, why use b+ tree as index node, how much data a node stores, how to specify the size, and the corresponding disk page.
4. If Redis has 100 million keys, will using the keys command affect online services?
5. Redis persistence methods, aod and rdb, how to implement it, append logs and backup files, do you know the underlying implementation principle?
6. What is the biggest difficulty encountered? How to overcome?
7. What is the future plan?
8. What do you want to ask me?

Tmall (four sides) pressure test + Mina + transaction + cluster + spike architecture

one side

1. The difference and applicable scenarios of common collections
2. What do concurrent containers know?
3. How to judge whether the linked list has a ring
4. How to implement concurrentHashMap
5. How cluster servers share application
6. JAVA network programming: the difference and connection between BIO, NIO and AIO
7. Jvm memory model jmm knows all about
8. JAVA garbage collection, the difference between the marking algorithm and the copy algorithm, what occasions are they used for?
9. The difference between http and https, the difference between http1.x and http2.0, the difference between SSL and TSL
10. The difference between GC, G1 and ZGC
11. The difference between B+ tree and B tree, and the difference between red and black trees
12. The difference between memory leak and memory overflow
13. How long is the life cycle of the session
14. How much do you know about the Mina framework? (Because I used Mina in the project, I mentioned this part)

Two sides

1. java cas principle
2. What are the parameters of the JAVA thread pool, and what issues should be considered if you design a thread pool by yourself?
3. The underlying implementation of Java's lock?
4. What are the advantages of mysql database default storage engine
5. MySQL's transaction isolation level, what problems are solved respectively.
6. Four tables record grades, each with about 100,000 records, how to find the students with the best grades
7. What are the common load balancing algorithms
8. If Redis has 100 million keys, will using the keys command affect online services?
9. Redis persistence methods, aod and rdb, how to implement it, append logs and backup files, do you know the underlying implementation principle?

Three sides

1. Please draw a distributed server cluster deployment diagram of a complete large-scale website
2. Multiple RPC requests come in, how does the server handle concurrency?
3. Talk about the sentinel mechanism of Redis
4. How much data does the database sub-database sub-table generally need?
5. How to ensure that the database is consistent with the redis cache
6. How is the message queue used in the project? What specific business scenarios are used?
7. Which JVM-related analysis tools have you used? Are there specific performance tuning steps?
8. How to do MySQL slow sql optimization in general? In addition to other methods to optimize?
9. Online server monitoring indicators, which indicators do you think need the most attention? why?
10. How to do stress test, anti-stress method
11. How to design the spike module

HR face

1. Self introduction
2. How would you rate your previous 3 interviews
3. What do you think of yourself, what is your biggest core competitiveness
4. Future career plan
5. What kind of understanding of Ali's technology atmosphere, and which Ali's open source libraries have been used
6. What is the expected salary
7. Finally, what do you want to know

The above is the interview process of some well-known big companies. The restriction has entered the peak of job hunting and recruitment. The editor is here to share the summary of high-frequency interview questions for Java interviews (including Java collection, JVM, concurrency and multi-threading, Spring, MyBaits, Micro Services, Dubbo, Kakfa, middleware, Redis, database, design patterns, etc.) are organized and shared with everyone for free.

How to get answers to Java high-frequency interview questions: follow the editor and click to enter the secret code: short book .

I hope that everyone can bring these questions and answers to analyze, so that you can study in a targeted manner, know yourself and your opponents in the interview, and be victorious.