The latest 2020 BAT--java800+ collection interview review, if you can master 80%, go to BATJTMD

Jin Jiu Yin Shi is commonly known as the golden period of job-hopping. Many students want to take advantage of this time to get high salaries, work in more powerful companies, get to know more talents, and enhance their competitiveness in the workplace.

How can we pass the T interviewer's assessment? How to become an Offer harvester?

I said before that there is one of the most direct announcements for harvesting Offer: Offer=Hardly passed the BAT interviewer's assessment? How to become an Offer harvester?

I said before that there is one of the most direct announcements for Reaping Offer: Offer=hard power * soft power * a good mentality, one of the three is indispensable.

1. Hard power

The hard power mentioned here is the true accumulation of technology.

How to reflect your technical strength? My total is divided into two aspects: technical depth and technical breadth.

The breadth of technology is that you are familiar with the use and basic principles of the technology. Generally, interviewers will ask a lot of technical points in the first round of interviews to assess whether you can use them correctly.

Technically in-depth, in layman's terms, is to understand the comparison of advantages and disadvantages, the horizontal and vertical comparison of similar products, and very important application scenarios while in-depth technical principles. On this point, I will share here. For example: Message Queuing MQ, which MQs are available in the market, RabbitMQ, RocketMQ, ActiveMQ...etc. Their respective architecture design, comparison of advantages and disadvantages, and respective application scenarios (concurrency and usage comparison, etc.). And MQ's message deduplication, how to ensure that the message is not lost, etc. In this way, follow the topic of MQ to thoroughly assess your mastery of message queue middleware.

02 What does technical strength include

• network programming
• Http和Https
• OSI7 layer model
• Network security protection: CSRF, XSS, etc.
• Algorithm and data structure
• Array, linked list, binary tree , queue
• Red-black tree, AVL tree, Hash tree, Tire tree, B tree, B+ tree
• Various sorting algorithms and complexity analysis ( fast sorting, merging, heap )
• Binary search and various variants of binary search
• Handwriting algorithm etc.
• JVM
• Memory reclamation algorithm
• Garbage collector
• Performance tuning
•  
• Concurrent programming
• Multithreading
• NIO
• Concurrent container
• Concurrency tools
• ...Wait
• database
• mysql and nosql
• Indexes, slow queries, transactions
• Big data solution: sub-database and sub-table, read-write separation, data synchronization between master and slave
•  
• Distributed architecture design
• Redis asks more (it is recommended to focus on it)
• Message queue Kafka, RabbitMQ, RocketMQ (Ali will ask)
• Microservices: Dubbo, Spring Cloud, etc.
• Load balancing
• Distributed theory: CAP, BASE, etc.
• Application system split
• Distributed locks, distributed transactions, distributed global unique ID... etc.

03Soft Power

Soft power is also particularly important in the interview process (sometimes it is more important), mainly refers to the communication with the interviewer, the way of elaborating and expressing a question, logical thinking ability, etc.

Smiles throughout the interview process, project descriptions need to be rigorously stated, and personal strengths and weaknesses should basically be revealed casually... etc. These are actually the embodiment of soft power.

Technical interview questions

MySQL 55 interview questions

1. A table with an ID auto-incrementing primary key. After inserting 17 records, delete the 15, 16, 17 records, restart Mysql, and insert a record. Is the ID of this record 18 or 15?
2. What are the technical characteristics of Mysql?
3. What is the Heap table?
4. What is the default port of Mysql server?
5. Compared with Oracle, what are the advantages of Mysql?
6. How to distinguish FLOAT and DOUBLE?
7. Distinguish between CHAR_LENGTH and LENGTH?
8. Please briefly describe the names of the four transaction isolation levels supported by InnoDB in Mysql and the differences between each level?
9. What is the usage of ENUM in Mysql?
10. How to define REGEXP?
11. What is the difference between CHAR and VARCHAR?
12. What can be the string type of the column?
13. How to get the current Mysql version?
14. What storage engine is used in Mysql?
15. What is the Mysql driver?
16. What does TIMESTAMP do on the UPDATE CURRENT_TIMESTAMP data type?
17. What is the difference between primary key and candidate key?
18. How to use Unix shell to log in to Mysql?
19. What is myisamchk used for?
20. What are the method commands for MYSQL database server performance analysis?
21. How to control the maximum size of the HEAP table?
22. What is the difference between MyISAM Static and MyISAM Dynamic?
23. What is a federated table?
24. If a table has a column defined as TIMESTAMP, what will happen?
25. When the column is set to AUTO INCREMENT, what happens if it reaches the maximum value in the table?
26. How can I find out which auto increment was assigned during the last insert?
27. How do you see all the indexes defined for the table?
28. What do% and _ in the LIKE statement mean?
29. How to convert between Unix and Mysql timestamps?
30. What is the column comparison operator?
31. How do we get the number of rows affected by the query?
32. Is Mysql query case sensitive?
33. What is the difference between LIKE and REGEXP operations?
34. What is the difference between BLOB and TEXT?
35. What is the difference between mysql_fetch_array and mysql_fetch_object?
36. How do we run batch mode in mysql?
37. Where will the MyISAM table be stored and also provide its storage format?
38. What are the different tables in Mysql?
39. What is ISAM?
40. What is InnoDB?
41. How does Mysql optimize DISTINCT?
42. How to input characters as hexadecimal numbers?
43. How to display the first 50 rows?
44. How many columns can be used to create an index?
45. What is the difference between NOW() and CURRENT_DATE()?
46. What kind of objects can be created using the CREATE statement?
47. How many TRIGGERS are allowed in Mysql table?
48. What is a non-standard string type?
49. What are common SQL functions?
50. Explain the access control list
51. Does MYSQL support transactions?
52. What field type is good for recording currency in mysql
53. Under what circumstances are MYSQL data tables easily damaged?
54. What are the mysql tables about permissions?
55. What kind of locks are there in Mysql?

JVM 20 interview questions

1. The memory model and partitions need to be detailed on what to put in each area.
2. Partitions in the heap: Eden, survival (from + to), old age, their own characteristics.
3. Object creation method, object memory allocation, object access location.
4. Two judgment methods of GC
5. What is SafePoint
6. The three collection methods of GC: the principles and characteristics of mark removal, mark sorting, and copying algorithms. Where are they used? If you are asked to optimize the collection method, what ideas do you have?
7. What are the GC collectors? Features of CMS collector and G1 collector.
8. When do Minor GC and Full GC happen respectively?
9. Several commonly used memory debugging tools: jmap, jstack, jconsole, jhat
10. Several processes of class loading?
11. JVM memory is divided into several areas, what is the role of each area?
12. How to judge whether an object is alive? (or how to judge GC objects)
13. Briefly describe the java garbage collection mechanism?
14. What are the methods of garbage collection in java?
15. java memory model
16. java class loading process?
17. Briefly describe the java class loading mechanism?
18. The class loader parent delegation model mechanism?
19. What are class loaders and what are the class loaders?
20. Briefly describe the java memory allocation and recovery strategy and Minor GC and Major GC

Redis 46 interview questions

1. What is Redis?
2. What are the advantages of Redis over memcached?
3. Which data types does Redis support?
4. What physical resources does Redis consume?
5. What is the full name of Redis?
6. What kinds of data elimination strategies does Redis have?
7. Why doesn't edis officially provide a Windows version?
8. What is the maximum storage capacity for a string value?
9. Why does Redis need to put all data in memory?
10. What should the Redis cluster solution do? What are the options?
11. Under what circumstances will the Redis cluster solution cause the entire cluster to be unavailable?
12. There are 2000w data in MySQL and only 20w data in redis. How to ensure that the data in redis is hot data?
13. What are the suitable scenarios for Redis?
14. What are the Java clients supported by Redis? Which one is the official recommendation?
15. What is the relationship between Redis and Redisson?
16. What are the advantages and disadvantages of Jedis and Redisson?
17. How to set password and verify password in Redis?
18. Talk about the concept of Redis hash slot?
19. What is the master-slave replication model of Redis cluster?
20. Will write operations be lost in the Redis cluster? why?
21. How is replication between Redis clusters?
22. What is the maximum number of nodes in a Redis cluster?
23. How to choose a database for Redis cluster?
24. How to test the connectivity of Redis?
25. What is the use of pipelines in Redis?
26. How to understand Redis transaction?
27. What are the commands related to Redis transactions?
28. How does Redis optimize memory?
29. How does the Redis recycling process work?
30. What algorithm does Redis use for recycling?
31. How does Redis do a large amount of data insertion?
32. Why do Redis partitions?
33. Do you know what Redis partitioning schemes are there?
34. What are the disadvantages of Redis partitioning?
35. How to expand Redis persistent data and cache?
36. Should distributed Redis be done at the early stage or at the later stage? why?
37. What is Twemproxy?
38. What clients support consistent hashing?
39. How is Redis different from other key-value stores?
40. What is the memory usage of Redis?
41. Are there any ways to reduce the memory usage of Redis?
42. How many keys can a Redis instance store at most?
43. Redis common performance problems and solutions?
44. What kinds of persistence methods does Redis provide?
45. How to choose a suitable persistence method?
46. Will the modified configuration take effect in real time without restarting Redis?

Multi-threaded 48 interview questions

1. Three elements of concurrent programming?
2. What are the ways to achieve visibility?
3. The value of multithreading?
4. What are the ways to create threads?
5. Comparison of the three ways of creating threads?
6. Thread state flow diagram
7. Java thread has five basic states
8. What is a thread pool? What are the ways to create it?
9. Creation of four thread pools
10. Advantages of thread pool?
11. What are the commonly used concurrency tools?
12. The difference between CyclicBarrier and CountDownLatch
13. The role of synchronized?
14. The role of the volatile keyword
15. What is CAS
16. CAS problem
17. What is Future?
18. What is AQS
19. AQS supports two synchronization methods
20. What is ReadWriteLock
21. What is FutureTask
22. The difference between synchronized and ReentrantLock
23. What is optimistic lock and pessimistic lock
24. How does thread B know that thread A has modified the variable
25. Synchronized, volatile, CAS comparison
26. What is the difference between sleep method and wait method?
27. What is ThreadLocal? What is the use?
28. Why wait() method and notify()/notifyAll() method should be called in synchronized block
29. What are the methods for multi-thread synchronization?
30. Thread scheduling strategy
31. What is the concurrency of ConcurrentHashMap
32. How to find which thread uses the longest CPU in Linux environment
33. Java deadlock and how to avoid it?
34. The cause of deadlock
35. How to wake up a blocked thread
36. How immutable objects help multithreading
37. What is multi-threaded context switching
38. What will happen if the thread pool queue is full when you submit a task
39. What is the thread scheduling algorithm used in Java
40. What is Thread Scheduler and Time Slicing?
41. What is spin
42. What is the Lock interface in the Java Concurrency API? What are its advantages over synchronization?
43. Thread safety of singleton mode
44. What does Semaphore do
45. What is the Executors class?
46. Thread class construction method, static block is called by which thread
47. Synchronization method or synchronization block, which is the better choice?
48. What is the exception caused by too many Java threads?

Message queues, Kafka, MQ, databases, algorithms, data structures, etc. will not be shown one by one (there is a list of interview questions at the end of the article)

 

The above is a summary of the BAT interview experience , the following Java interview questions answers, BATJ and other major Internet companies' interview truth.

 

 

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