This article covers the real Java interview questions of Alibaba, Tencent, ByteDance, JD.com, Huawei and other big companies. Whether you are interviewing big companies or ordinary Internet companies, these interview questions are definitely helpful to you. After all, big companies It must be the benchmark for the development of the industry, and interviewers from many companies will also study interview questions from major companies.

At the same time, this year's algorithm interview will definitely be asked, and the algorithm is not useful only on the back of the test. It requires mathematical and logical thinking. Therefore, the editor will prepare a very high-quality algorithm study for everyone at the end of the article The manual, the focus is on learning the thinking method, not much to say, just start with the selected real interview questions!

Due to the limitation of the length of the article, it is impossible to display all interview questions in text format. This article selects some interview questions for everyone

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Selected questions for Java interviews, architecture and actual documentation portal: https://docs.qq.com/doc/DRW1nUkdhZG5zeGVi

Java basics

1. What are the several data types in JAVA and how many bytes each occupy.

2. Can the String class be inherited and why.

3. If the hashCode() of two objects is the same, equals() must also be true, right?

4. Is String a basic data type?

5. What are the classes of manipulation strings in Java? What is the difference between them?

6. How many types of IO streams are in Java?

7. What is the difference between BIO, NIO and AIO?

8. What are the differences between which Map classes have been used, is HashMap thread safe, what Map is used concurrently, and their internal principles, such as storage method, hashcode, capacity expansion, default capacity, etc.

9. How to reverse the string?

10. Does an abstract class have to have abstract methods?

11. What are the differences between ordinary and abstract classes?

12. Can abstract classes use final modification?

13. What is the difference between ArrayList and LinkedList?

14. ConcurrentHashMap data structure (required)

15. Volatile role (required)

16. How does the Atomic class guarantee atomicity (CAS operation) (required)

17. Why use thread pool (required)

Redis

Application scenarios of Redis
Data types supported by Redis (required)
The data structure of zset jump table (required)
Redis data expiration strategy (required)
The specific implementation of Redis's LRU expiration strategy
How to solve the Redis cache avalanche and cache penetration problems
Redis persistence mechanism (required)
Why is Redis single-threaded?
What is cache penetration? How to deal with it?
How many ways are Redis persistence?
Why is Redis so fast? (Required)
How does Redis implement distributed locks?
How does Redis optimize memory?
What are the Redis elimination strategies?
What are the common performance problems of Redis? How to solve it?
What should I pay attention to when using Redis?

ZooKeeper

CAP theorem
ZAB agreement
Leader election algorithm and process
What is zookeeper?
How many deployment modes does zookeeper have?
How does zookeeper ensure the synchronization of the master and slave nodes?

Mysql

Basic elements of business
Transaction isolation level (required)
How to solve the problem of transaction concurrency (dirty reading, phantom reading) (required)
MVCC multi-version concurrency control (required)
What are binlog, redolog and undolog, and what are their functions
InnoDB row lock/table lock
The difference between myisam and innodb, when to choose myisam
Why choose B+ tree as index structure (required)
What things can be stored in the leaf nodes of the index B+ tree (required)
When the query will not go (expected) index (required)
How to optimize sql
explain how to parse sql
Principle of order by

JVM

Runtime data area (memory model) (required)
Garbage collection mechanism (required)
Garbage collection algorithm (required)
Minor GC and Full GC trigger conditions
GC中Stop the world（STW）
The characteristics and differences of each garbage collector
Parental Delegation Model
Relationship between JDBC and Parental Delegation Model
What is a complete GC process in JVM, how to promote the object to the old age, talk about the main JVM parameters you know

Spring

Implementation of Spring's IOC/AOP (required)
Realization of dynamic agent (required)
How does Spring solve circular dependencies (three-level cache) (required)
Spring's post processor
How to implement Spring @Transactional (required)
Spring's transaction propagation level
The connection and difference between BeanFactory and ApplicationContext

other

How to realize the current limit of high concurrent system
The design of high concurrency spike system
How to design load balancing

Operating system

The difference between process and thread
Several ways of process synchronization
Synchronization between threads
What is a buffer overflow. What is the harm and the reason
What kinds of states are there in the process
What is the difference between paging and segmentation

Multithreading

Several implementations of multithreading, what is thread safety
The principle and function of volatile, can it replace locks?
The difference between sleep and wait
The meaning of sleep(0)
The difference between Lock and Synchronized
What is the principle of synchronized and where is it generally used (for example, the difference between loading static methods and non-static methods)

supplement

In addition, some computer networks will be tested. Like message queues, RPC frameworks are rarely tested. Computer network is hierarchical, tcp/udp, three-way handshake and the like. The operating system is the process and the thread, the data structure of the process and how to communicate.

The sorting algorithm of the data structure is also more frequently tested, and you will be sure to write a quick sort by hand. The remaining algorithmic questions are accumulated by LeetCode. In fact, the algorithmic questions for non-algorithmic post exams are quite simple. Many questions are to check whether your intelligence is normal. The slightly more difficult ones involve some algorithmic ideas. According to the classification of LeetCode question types, you can basically complete one or two questions for each question Time to interview.

Next, I’m going to share notes on data structures and algorithms with you!

Data structure and algorithm notes

Dynamic planning and design

Data structure series

Algorithm Thinking Series

High-frequency interview questions series

computer technology

At last

Interviews are the most direct and effective way to change jobs and raise salaries. It is coming soon. Are you ready for interviews to build airplanes and work screws?

Having mastered these knowledge points, you can get a lot of eye-catching among candidates during the interview, crit 9999 points. Opportunities are reserved for those who are prepared. Only with sufficient preparation can oneself stand out among the candidates.

If you need this full version of the interview notes , you only need to support me in this article.