In order to get offers from several big companies, "retreat practice" finally got the analysis of the core interview questions of 15 senior Java engineers of Internet companies

At home, are you "retreating and practicing" worrying about the September and October job-hopping season? Some people are happy and others are sad. Whether you are happy or worried, learning is always good. No, the editor specially sorted out the autumn recruitment interview knowledge points + answers (JAVA post), and shared them for everyone to see~ The editor said today that there are 15 core interview questions for Java senior engineers from major Internet companies. ! content include:

Eat thoroughly and digest well, so that you will no longer be flustered in the job interview!

Note: There is a need for this "Interview Job-hopping Guide: Analysis of 498 Questions in the Core Interview for Java Senior Engineers from Internet Companies" (and more learning materials)

One-click triple + comment, then add my VX (tkzl6666) to receive it for free.

Java set questions and answer analysis

• The source code of HashMap, the principle of implementation, and how optimized HashMap is made in JDK8.
• How does the expansion of HaspMap expand, and why are they all 2 to the power of N?
• The difference between HashMap, HashTable and ConcurrentHashMap.
• Which performance is better under high concurrency, HashTable or ConcurrentHashMap, why, and how to achieve it.
• What are the security risks of HashMap if it does not handle thread safety under high concurrency, and what are the specific manifestations.
• The limited scope of the four modifiers in java.
• Methods in the Object class.
• The difference between interface and abstract class, note that JDK8 interface can be implemented.
• Two ways of dynamic proxy, and the difference.
• The way of Java serialization.
• The difference between pass-by-value and pass-by-reference, what is Java like, and is there any pass-by-reference.
• An ArrayList is deleted during the loop, will there be a problem, why?
• The @transactional annotation is invalid under what circumstances and why.
• What are the basic interfaces of the Java collection framework?
• What is the difference between HashSet and TreeSet?
• What is the underlying implementation of HashSet?
• How does LinkedHashMap work?
• Why does the collection class not implement the Cloneable and Serializable interfaces?
• What is the difference between Array and ArrayList? When should I use Array instead of ArrayList?
• What are the best practices for the Java collection framework?
• The elements in a set cannot be repeated, so what method is used to distinguish whether they are repeated or not? Should I use == or equals()? What is the difference between them?
• What are the Comparable and Comparator interfaces? List their differences
• The difference between Collection and Collections.

 

JVM and tuning 21 questions and answers analysis

• The memory structure of the JVM.
• The working process of JVM method stack, what is the difference between method stack and local method stack.
• How do references in the JVM stack relate to objects in the heap.
• You can learn about escape analysis techniques.
• Common algorithms of GC
• The garbage collection process of CMS and G1, which two of the various stages of CMS are Stop the world, and whether CMS will generate fragments, is the advantage of G1.
• The process and advantages of the parent delegation model.
• Commonly used JVM tuning parameters.
• When did the subject enter the old age?
• What is memory overflow, memory leak? What is the difference between them?
• What are the behaviors that cause class loading operations?
• Introduce the common tools provided by JVM
• What is the difference between Full GC, Major GC, and Minor GC?
• When is Full GC triggered?
• Under what circumstances will stack overflow
• Talk about strong references, soft references, weak references, phantom references and their relationship with gc
• What is the proportional distribution of Eden and Survivor? why?
• What is distributed garbage collection (DGC)? How does it work?
• What is the difference between a serial collector and a throughput collector?
• In Java, when can an object be garbage collected?

 

Concurrent programming 28 questions and answer analysis

Concurrency Collection: Interview Topics

The interview topic is divided into four parts, as follows

• Synchronized related issues
• ReentrantLock ReentrantLock and other explicit lock related issues
• Java thread pool related issues
• Java memory model related issues

1.1 Synchronized related questions (eight questions are organized here)

• Question 1: Have you used Synchronized? What is the principle?
• Question 2: You just mentioned acquiring the object's lock. What is this "lock"? How to determine the lock of an object?
• Question 3: What is reentrancy, and why is Synchronized a reentrant lock?
• Question 4: What optimizations has JVM made to Java's native locks?
• Question 5: Why is Synchronized an unfair lock?
• Question 6: What is lock elimination and lock coarsening?
• Question 7: Why is Synchronized a pessimistic lock? What is the principle of optimistic locking? What is CAS and what are its characteristics?
• Question 8: Is optimistic locking necessarily good?

 

1.2 ReentrantLock and other explicit lock related issues (eight questions)

• Question 1: Compared with Synchronized, what is the difference in the implementation principle of ReentrantLock?
• Question 2: So please talk about the AQS framework?
• Question 3: Please compare the similarities and differences between Synchronized and ReentrantLock as much as possible
• Question 4: How does ReentrantLock achieve reentrancy?
• Question 5: In addition to ReetrantLock, which concurrency tools have you been exposed to in JUC?
• Question 6: Please talk about ReadWriteLock and StampedLock.
• Question 7: How to synchronize Java threads with each other? What synchronizers do you know about? Please introduce them separately.
• Question 8: CyclicBarrier and CountDownLatch look very similar, please compare?

 

1.3 Java thread pool related questions (six questions)

• Question 1: How is the thread pool implemented in Java?
• Question 2: How many core construction parameters are needed to create a thread pool?
• Question 3: How are the threads in the thread pool created? Was it created at the beginning with the thread pool started?
• Question 4: Since it is mentioned that different thread pools can be created by configuring different parameters, what thread pools are implemented by default in Java? Please compare their similarities and differences.
• Question 6: How to submit threads in the Java thread pool?

 

1.4 Java memory model related questions (six questions)

• Question 1: What is Java's memory model, and how do threads in Java see each other's variables?
• Question 2: Please talk about the characteristics of volatile and why it can guarantee the visibility of variables to all threads?
• Question 3: Since volatile can guarantee the visibility of variables between threads, does it mean that operations based on volatile variables are concurrently safe?
• Question 4: Please compare the similarities and differences between volatile and Synchronized
• Question 6: Many people say that ThreadLocal should be used with caution. Talk about your understanding. What should I pay attention to when using ThreadLocal?

 

Spring hundred questions interview analysis

• What is the Spring framework? What are the main modules of the Spring framework?
• What are the benefits of using the Spring framework?
• What are the different types of events in the Spring framework?
• What design patterns are used in the Spring framework?
• What is Inversion of Control (IOC)?
• Please explain the IoC in the Spring framework?
• What is the difference between BeanFactory and ApplicationContext?
• How many ways to configure Spring?
• How to configure Spring based on XML configuration?
• How to configure Spring based on Java configuration?
• How to configure Spring with annotations?
• Please explain the life cycle of Spring Bean?
• What is the difference between the scope of Spring Bean?
• What are Spring inner beans?
• Are singleton beans in the Spring framework thread-safe?
• Please give an example of how to inject a Java Collection in Spring?
• How to inject a Java.util.Properties into Spring Bean?
• Please explain the autowiring of Spring Bean?
• Please explain the difference in auto-assembly mode?
• How to turn on annotation-based automatic assembly
• Please give an example to explain the @Required annotation?
• Please give an example to explain the @Autowired annotation?
• Please give an example of @Qualifier annotation?
• What is the difference between constructor injection and setting injection?
• What is the difference between FileSystemResource and ClassPathResource?
• BeanFactory 和 FactoryBean
• What does Spring IOC understand and its initialization process?
• BeanFactory 和 ApplicationContext？
• How is the life cycle of Spring Bean managed? What is the loading process of Spring Bean?
• If you want to implement Spring AOP, how do you do it?
• If you were to implement Spring IOC, what issues would you pay attention to?
• How does Spring manage transactions, transaction management mechanism?
• What are the different transaction propagation behaviors of Spring, and what are they used for?
• What design patterns are used in Spring?
• How does Spring MVC work?
• The principle of Spring cycle injection?
• How does Spring ensure the safety of Controller concurrency?

 

High frequency 35 questions SpringBoot (with analysis)

Spring Boot is the best Java framework in microservices. Thirty-five high-frequency Spring Boot interview questions are selected here to help better review and study.

• Question 1: What is the difference between Spring Boot, Spring MVC and Spring?
• Question 2: What is automatic configuration?
• Question 3 What is Spring Boot Stater?
• Question 4 Can you give an example to explain more about Statusers?
• Question 5 What other Starter Project Options does Spring Boot provide?
• Question 6 How does Spring quickly create product-ready applications?
• Question 7 What is the easiest way to create a Spring Boot Project?
• Question 8 Is Spring Initializr the only way to create Spring Boot Projects?
• Question 9 Why do we need spring-boot-maven-plugin?
• Question ten: How to use SpringBoot to automatically reinstall my application?
• Question 11 What is an embedded server? Why should we use embedded servers?
• Question 12: How to add general JS code in Spring Boot?
• Question 13 What is Spring Data?
• Question 14 What is Spring Data REST?
• Question 15 How to use path=”users”, collectionResourceRel=”users” with Spring Data Rest?
• Question 16 What happens in the background when a Spring Boot application runs as a Java application?
• Question 17 Can we use jetty instead of tomcat in spring-boot-starter-web?
• Question 18: How to use Spring Boot to generate a WAR file?
• Question 19: How to deploy to different servers using Spring Boot?
• Question 20 What is the difference between RequestMapping and GetMapping?
• Question 21 Why do we not recommend using Spring Data Rest in actual applications?
• Question 22: How to change the package name of a project in Spring Initializer?
• Question 23: Where can I find the complete list of properties that can be configured for application.propertierde?
• Question 24 What are the differences between JPA and Hibernate?
• Question 25: Where should the business boundary start?
• Question 26: What dependencies are needed to start a JPA application connected to the in-memory database H2 using Spring Boot?
• Question 27: How to choose Hibernate as the default implementation of JPA without any configuration?
• Question 28 Where is the specified database connection information? How does it know to automatically connect to H2?
• Question 29 How do we connect to an external database like MySQL or Orcale?
• Question 30 What is the name of the default H2 database configured by Spring Boot?
• Question 31 Why is the default database name testdb?
• Question thirty-two if H2 is not in the classpath, will the above situation occur?
• Question 33 Can you give an example of using ReadOnly as transaction management?
• Question 34 What are the requirements for configuration files?
• Question 35: How to use the configuration file to configure the configuration of a specific environment through Spring Boot?

 

Analysis of 23 design patterns

 

Distributed high concurrency architecture analysis (message queue, sub-database and sub-table, transaction, high availability, micro-service architecture)

• Dubbo's underlying implementation principle and mechanism
• Describe the detailed process of a service from being published to being consumed
• How to do service governance in distributed systems
• The concept of interface idempotence
• How message middleware solves the problem of message loss
• How to deal with Dubbo service request failure
• Will the reconnection mechanism cause errors?
• Understanding of distributed transactions
• How to achieve load balancing and what algorithms can be implemented?
• What is the purpose of Zookeeper and the principle of election?
• Data is split vertically and horizontally.
• Zookeeper principle and applicable scenarios
• zookeeper watch mechanism
• How to deal with redis/zk node downtime
• How to achieve a unique serial number in a distributed cluster
• How to make a distributed lock
• Which MQs have been used, how to use them, what are the advantages and disadvantages compared with other mqs, is the connection of MQ thread safe?
• How to ensure that the data of the MQ system is not lost
• List the database sub-database sub-table strategies you can think of; after sub-database sub-table, how to solve the problem of full table query
• Zookeeper's election strategy

 

MySQL high-frequency 20 questions analysis

• The four characteristics of transactions (ACID) atomicity, consistency, isolation, and durability?
• Concurrency of transactions? Transaction isolation level, what problems each level will cause, which level is MySQL by default?
• What is the difference between the three common MySQL storage engines (InnoDB, MyISAM, MEMORY)?
• MySQL's MyISAM and InnoDB storage engines, transaction and lock levels, and their respective applicable scenarios?
• What is the order in which the different elements of the query statement (where, jion, limit, group by, having, etc.) are executed?
• What is a temporary table and when is the temporary table deleted?
• The difference between MySQL B+Tree index and Hash index?
• SQL query statement determines which type of index to create? How to optimize the query?
• The difference between clustered index and non-clustered index?
• What are the locks (optimistic locks, pessimistic locks), and how to add exclusive locks when selecting?
• What are the differences between non-relational databases and relational databases, and what are the advantages?
• Database three paradigms, design data tables according to a certain scene?
• 7 problems of database read-write separation, master-slave replication, master-slave replication analysis?
• Use explain to optimize sql and index?
• How to solve MySQL slow query?
• What are inner joins, outer joins, cross joins, Cartesian products, etc.?
• What locks does mysql have, the principle of deadlock determination and specific scenarios, and how to solve the deadlock?
• What are the usage scenarios of varchar and char?
• mysql high concurrency environment solution?
• Transaction recovery mechanism (REDO log and UNDO log) when the database crashes?

 

Redis45 questions and answers analysis

• Why use redis / why use cache (high performance, high concurrency)
• Why use redis instead of map/guava for caching?
• 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 is hot data? )
• Redis persistence mechanism ( how to ensure that the data can be restored after redis hangs and restarts )
• redis transaction
• Redis common exceptions and solutions ( cache penetration, cache avalanche, cache warm-up, cache degradation )
• Common application scenarios in a distributed environment ( distributed locks, distributed self-incrementing ID )
• Redis cluster mode ( master-slave mode, sentinel mode, Cluster cluster mode )
• 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?

 

Many people lament that "learning is useless". In fact, the reason why the theory of uselessness arises is because what they want does not match what they have learned, which means that they have not learned enough. Whether it is studying or working, there should be initiative, so if you have the dream of a big factory, you must work hard to realize it yourself.

Finally, once again, if you want to switch to an interview without being flustered, you should "retreat and practice" at home and read through these " Analysis of Core Interview Questions for Senior Java Engineers of Internet Companies "

One-click triple + comment, then add my VX (tkzl6666) to receive it for free.

The above learning materials are all free of charge. Finally, I wish you all good health and successfully get your favorite offer!