Alibaba has four years of backstage, and wants to change jobs. It has been difficult for 4 years, and has successfully received the offer from the development post.

I have stayed in Ali for four years and I am currently on P6. I feel that I have encountered a bottleneck and P7 has not been able to get up. That’s why I decided to switch to ByteDance.

Interview preparation

Whether it is school recruitment or social recruitment, various interviews and written examinations cannot be avoided. How to prepare for these things is extremely important. After strategizing, the decisive victory is thousands of miles away! Instead of fighting unprepared battles, I think everyone can prepare for the interview from the following aspects:

1. Introduce yourself. (Introduce your own project experience and some specialties instead of simply introducing your preferences, etc.)

2. What knowledge points may be involved in the interview, and those knowledge points are the key points.

3. What questions are frequently asked during the interview, and how should I answer them during the interview.

4. How to write your own resume.

"80% of the offer is in the hands of 20% of the people" is not unreasonable. Although strength occupies a large proportion of the factors that determine your success in the interview, if you have bad mentality or bad luck, you still cannot get a satisfactory offer. Let’s leave luck aside. Take the mentality as an example. Don’t be discouraged or doubt your abilities because of an interview failure. After the interview fails, sum up the reasons for the failure. Later, you will find that you will become stronger and stronger.

In addition, the important points for everyone to be clear are:

1. You must be cautious about what you write on your resume. This may be a place where interviewers ask a lot of questions;

2. It is very important to show your project experience perfectly.

Common interview questions and scope are as follows. The required information in the text and more Java architecture information can be obtained here.

Java basics

• The difference between overloading and rewriting
• What is the difference between String and StringBuffer and StringBuilder? Why is String immutable?
• Automatic boxing and unboxing
• == and equals
• final keyword
• Common methods of Object class
• Exception handling in Java
• Get the two commonly used methods of keyboard input
• What is the difference between an interface and an abstract class

Multithreading and concurrency

• AQS principle
• How AQS shares resources
• The bottom layer of AQS uses the template method pattern
• Talk about your understanding of the synchronized keyword
• Tell me how I use the synchronized keyword, is it used in the project?
• Talk about the underlying principle of the synchronized keyword
• Tell me what optimizations have been made at the bottom of the synchronized keyword after JDK1.6. Can you introduce these optimizations in detail?
• Talk about the difference between synchronized and ReenTrantLock
• Talk about the difference between the synchronized keyword and the volatile keyword
• Why use thread pool?
• Implement the difference between Runnable interface and Callable interface
• What is the difference between execute() method and submit() method?
• How to create a thread pool
• Introduce Atomic Atomic Class
• What are the 4 types of atomic classes in the JUC package?
• Talk about the use of AtomicInteger
• Can you give me a brief introduction to the principle of the AtomicInteger class

Collection frame

• Similarities and differences between Arraylist and LinkedList
• The difference between ArrayList and Vector
• The underlying implementation of HashMap
• The difference between HashMap and Hashtable
• Why is the length of HashMap a power of 2
• HashMap multi-threaded operation causes infinite loop problem
• The difference between HashSet and HashMap
• The difference between ConcurrentHashMap and Hashtable
• The specific implementation of ConcurrentHashMap thread safety/underlying specific implementation

JVM

• Is there a memory leak in Java, briefly?
• Describe the principle mechanism of JVM loading Class files?
• What is the tomcat class loading mechanism?
• The class loader parent delegation model mechanism?
• Common garbage collection problems
• What is GC? Why do we need GC?
• Briefly describe the Java garbage collection mechanism?
• How to judge whether an object is alive?
• The advantages and principles of garbage collection, and consider 2 types of recycling mechanisms?
• What are the methods of garbage collection in Java?
• Tell me about the performance evaluation and test indicators you understand?
• What are the commonly used performance optimization methods?

MySQL

• Tell me about my understanding of the two common storage engines of MySQL: MyISAM and InnoDB?
• Do you understand the database index?
• Why can index improve query speed?
• How does Mysql add indexes to table fields?
• What are the common optimization methods for large tables?

Network programming and operating system

• The difference between TCP and UDP protocols
• Enter the URL address in the browser ->> The process of displaying the homepage
• The relationship between various protocols and HTTP protocol
• HTTP long connection, short connection
• TCP handshake three times and wave four times (frequent interviewers)
• Briefly introduce the Linux file system?
• Do you understand some common Linux commands?

Spring

• The scope of Spring Bean
• Isolation level in Spring transaction
• Transaction propagation behavior in Spring transaction
• What is AOP?
• What is IOC?

distributed

• Why use redis cache?
• Why use redis instead of map/guava for caching?
• What is the difference between redis and memcached?
• Redis common data structure and usage scenario analysis? (String, Hash, List, Set, Sorted Set)
• redis set expiration time
• Redis memory elimination mechanism (There are 2000w data in MySQL and only 20w data in Redis. How to ensure that the data in Redis are all hot data?)
• Redis persistence mechanism (how to ensure that the data can be restored after redis is hung up and restarted)?
• redis transaction
• Cache avalanche and cache penetration problem solutions
• How to solve Redis's concurrent competition Key problem
• How to ensure data consistency between the cache and the database when it is double-written?
• What is a message queue? Why use message queues?
• Improve system performance through asynchronous processing (peak clipping, reduce response time)
• Reduce system coupling
• Some problems caused by the use of message queues
• JMS two message models
• JMS five different message body formats
• Comparison of common message queues
• What is Dubbo? Why use Dubbo?
• What is RPC? What is the principle of RPC?
• How does Dubbo work?
• Explain what is load balancing?
• Take a look at the load balancing strategy provided by Dubbo?
• Is zookeeper down and directly connected to dubbo?

Summary of experience

1. Be cautious about what you write on your resume, and you must be very familiar with the things on your resume. Because under normal circumstances, the interviewer will ask according to your resume;

2. It is also very important to have a good project. This is likely to be a place where interviewers will ask a lot of questions, so before the interview, review the projects you have done;

3. Talk to the interviewer about basic knowledge such as the use of design patterns, the use of multi-threading, etc., which can be combined with specific project scenarios or how you use them in daily life;

4. It is recommended to know in advance the values ​​of the company you want to interview, and to judge whether you are suitable for this company.

In addition, I personally feel that the interview is also like a brand new journey. Failure and victory are common things. Therefore, I advise you not to become discouraged and lose your fighting spirit because of the interview failure. Don't be complacent because you passed the interview. What awaits you is a better future, keep on working hard!

At last

In view of the knowledge on the above system knowledge map, I summarized most of the interview questions and answers involved in the Internet company java programmer interview. Documents and architecture video materials are shared for free with everyone (including Dubbo, Redis, Netty) , Zookeeper, Spring cloud, distributed, high concurrency and other architecture technical materials), I hope to help you review before the interview and find a good job, and also save everyone’s time to search for materials on the Internet to learn. You can also follow me There will be more dry goods to share in the future.

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Interview answer + source code actual combat PDF + spring100 set + design pattern

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