1. Jumei
Java memory management
HashMap HashTable ConcurrentHashMap LinkedHashMap The difference between
the use and meaning of asynchronous mode
Write string reversal function
final static volatile and other modifier usage
The "private message" function in social networking sites requires high concurrency, scalability, and so on. Draw an architecture diagram and a brief description.
Commonly used design patterns, and focus on the observer pattern.
MVC mode, that is, the purpose of common MVC framework
message middleware, and some message middleware that I have used.
Mysql index type
The difference in internal mechanism between general index and joint index Elasticsearch's inverted index (get a piece of information, currently big data companies have
basically begun to adopt ElasticSearch) Redis list structure related operations
redis cluster application and advantages Disadvantages
Given an input string of unknown length (which may be very large), design a scheme
to sort repeated characters. Commonly used sorting algorithms, fast sorting, merging, and bubbling. The optimal time complexity of fast sorting, the worst complexity. The optimization scheme of bubble sorting.
The time complexity and advantages of binary search.
How to complete the reverse sorting of a built TreeSet.
About the multi-threaded architecture model, and continue to ask the reactor architecture model. The advantages and disadvantages of various models.
I talked about the architecture of the game server that I had participated in the design.
How to monitor the performance of the application server, continue to ask, compare various methods. Is there any point to pay attention to when using redis?
Such as the 1k problem of redis, the recommended naming method for redis keys, etc. Many threads (maybe different machines) need to
wait for coordination between each other to complete a certain kind of work. Ask how to design this coordination scheme. The
second round of interviews for wait and notify of java synchronization mechanism :
introduced the architecture diagrams of the two projects that have been done.
How to form a project team from 0-1.
How to choose technology selection.
How to meet demand.
How do I answer the written test questions? Linux simple commands.
As a leader, in the development process, there are any specifications.
2. Vipshop
1. Why is hashmap unsafe (I forgot this)
2. Concurrent hash implementation (default capacity, when to expand, how to expand)
3. Thread pool (what is included, core, max contact)
4. How to achieve load balancing, what algorithms are there can be realised?
5. Synchronized principle
6. Volatile principle
7. Jmm (main memory, working memory [cache line or something], happens-before,)
8. What are the lock-free data structures? The principle of lock-free implementation?
9. Design mode (decorator design mode, agent mode, singleton mode, factory mode (3 types))
10. Dubbo design ideas, netty principle
11. The process of an rpc request
12. How does MySQL create a reasonable index and how to optimize the index ?
13. How does b+tree split, when is it split, and why is it balanced?
14. MySQL transaction implementation principle, ACID implementation principle
15. How does MySQL optimize table scan? (Scanning area, because the area is 64 consecutive pages, random scanning can be avoided)
16. Algorithm: There are 3n+1 numbers, of which 3n are repeated, and only 1 is not repeated. How to find out? (Recursive method)
17. If you still ask, you may ask (how to receive a network packet, how to optimize file io, network io, suggest that I read more io and
network information)
3. Baidu:
The file structure of MySQL InnoDB storage
How is the index tree maintained?
Database self-incrementing primary key possible problem Redis concurrency competition problem How to solve the problem of understanding the CAS operation of Redis transactions? Analyze
the implementation principle of thread pool and thread scheduling process
. There are several ways of dynamic proxy
implementation of Spring AOP and IOC.
Why CGlib way can interface Realize a proxy? The underlying implementation principle and mechanism of
RMI and the proxy model
Dubbo
describe the detailed process of a service from being published to being consumed. In terms of algorithm, a simple array in-situ de-duplication problem is investigated, and
how the distributed system is implemented by discarding the tail elements of the array.
The concept of the idempotence of the governance interface.
Maven has version conflicts. How to solve the
JVM garbage collection mechanism, when to trigger MinorGC and other operations?
The memory collection strategy of the young and old generations,
the proportional allocation of Eden and Survivor, etc.
The difference between Synchronized and Lock
4. Alibaba:
JVM memory generation
Java 8 memory generation improvements In-
depth analysis of Classloader, parental delegation mechanism
JVM compilation optimization
understanding of Java memory model, and its application in concurrency
Instruction reordering, memory fence and other
HashMap concurrency issues
understand LinkedHashMap applications you
come across what design patterns at work, is how to apply
5. Youku Tudou:
TCP/IP protocol
Long connection and short connection
mapreduce process
Time complexity of multiple merging
massive url deduplication problem
Java NIO use
Principle
of inverted index Understanding of word segmentation technology
6. Sohu News:
How does the message middleware solve the problem of message loss
? How to deal
with the failure of Dubbo's service request. Will the reconnection mechanism cause errors
? Understanding of distributed transactions. In-
depth analysis of several design patterns
7.58 Go to the market:
HTTP request message format Spring's transaction implementation principle Actual scenario problems, how to sort and de-
duplicate a large amount of user data in memory How to add and delete cache machines have the least impact on the system
, and several ways to achieve Redis persistence by consistent hashing
Redis Cache invalidation strategy solves the actual scene problem, the typical TOK problem actual scene problem, how to sort the massive login logs
and handle SQL operations, mainly the application of indexes and aggregate functions
8. Gome Online
SQL statement writing
MySQL optimization
Spring row-level lock
Spring-derived related other components Sorting out
several RMI protocols and implementing framework
BTree-related operations
Database lock table related processing
Investigating the problem of jumping
9.JD
The first round of interviews:
The realization principle of Java thread pool
whether threads can be shared. How the thread pool is shared by threads.
The memory structure of the JVM.
The realization principle of the Java lock mechanism (mainly drawing the monitor diagram).
How does Spring configure transactions (specifically say some key xml elements).
MySQL index type, how to store the B+ tree, and what is stored in each node.
What are the data structures of Redis.
How to apply the principle of opening and closing.
The realization principle of ConcurrentHashMap.
The state diagram of the thread.
The project architecture diagram designed before.
Some knowledge of data layer sub-database sub-table.
If someone maliciously creates an illegal connection, how to solve it.
Multi-threaded memory view (thread memory, main memory), and memory visibility.
Understanding of the volatile keyword.
The second round of interview:
How do I consider some design principles in programming, specifically discussing the opening and closing principles, and the application in work.
Detailed design and discussion of the project that I am most proud of.
Update problem after cached data expires.
How to design a class, mainly discusses the problem of class granularity.
Summary: For large companies, as long as it is a technical job interview, they still pay more attention to programming foundation, including but not limited to: on-site whiteboard
programming, basic sorting and search algorithms, Java foundation and concurrent package related classes, multi-threaded mode, Socket, etc. Wait. Working years is a
double-edged sword. The more experience you have, the higher the demands of others from you. Therefore, if your working years are not in proportion to your work experience
, it is difficult to get a senior position. When the candidates senior development positions, comparatively speaking, there will be more open-ended questions on these issues
often revolve around items on the resume, the more large companies, on the issue of a single point more in-depth, but not specifically requested The "breadth
" of your knowledge . Therefore, the phrase "knowledge breadth is a by-product of knowledge depth" is quite reasonable. In the usual process
of making a product or project , it must be summarized. It is not limited to a technical summary, but also includes a summary of the way of thinking, lessons, and the pros and cons of the solution to the problem