The salted fish has been transmitted for 5W times, and the latest spring recruit face-to-face test questions of bytes have been leaked

Java One side is basically basic questions , The same is CURD Live , Who is more skilled , For example, the following interview questions , The more proficient the eight part essay is, the easier it is to pass Java interview .

The following will give you a detailed introduction to the necessary questions of each technical point ！

One 、Java Basics

1.JDK Dynamic proxy sum CGLIB Dynamic proxy differences
2. The difference between static agent and dynamic agent
3.ArrayList and LinkedList What's the difference? ？
4. The difference between rewriting and overloading
5.Java 8 What new features have been added to the interface ？
6. Abstract classes and interfaces （Java7） The difference between
7. Why would there be hashCode
8.hashCode() Introduce
9.hashCode And equals ( important )
10.Java What are the types of anomalies in the ？
11. What are the classifications of internal classes
12. What is an inner class ？
13. What is the return value of a method ？ What is the function of the return value ？
14. How is the static method different from the instance method ？
15. The difference between static variables and instance variables
16. What are the characteristics of construction methods ？
17. stay Java The function of a construction method that does not work and has no parameters is defined in
18.break ,continue ,return The difference and function of
19.static matters needing attention
20.static Application scenarios
21.static What's unique about
22.static The main meaning of being
23.this And super The difference between
24.super Keyword usage
25.String What are the common methods of class ？
26.char Can a Chinese character be stored in the type variable , Why? ？
27. Can I inherit String class ？
28. Two objects have the same value (x.equals(y) == true), But it can be different hash code, That's right incorrect ？
29. Constructors （constructor） Whether it can be rewritten （override）？
30. Talk about your understanding of polymorphism ？
31.Java What is the mechanism of realizing polymorphism in ？
32.new The process of an object and clone The difference between an object ？
33. Deep and shallow clones ？
34.Java Why do you use clone？
35.Java What are the classes of the operation strings in ？ What's the difference between them ？
36.String str = “i” and String str = new String(“1”) Are they exactly alike? ？
37.final finally finalize The difference between
38.final What's the usage? ？
39.Java What are the data types
40. What is? Java notes
41. Calculate with the most efficient method 2 multiply 8？
42.Math.round(11.5) How much ？Math.round(-11.5) How much ？
43.& and && The difference between ？
44.Java Is there any goto？
45.float f=3.4; Whether it is right ？
46. Access modifier public,private,protected, And not to write （ Default ） The difference of time ？
47.Java What are the characteristics of language
48. What is? Java Main class of program ？ How the main classes of applications and applets differ ？
49. Let's talk about the four features of the object

I specially sorted out these interview questions , cover Java Basics 、 aggregate 、 Concurrent 、MySQL、Kafka Wait for high-frequency knowledge points , The first edition has 16 swastika , And it is still improving , It's updated every month .

Let's take a look at the catalog .

Two 、Java IO

1.IO The underlying principle of multiplexing
2. What does buffer mean ？
3. What does the channel mean ？
4. Sync 、 asynchronous 、 Blocking 、 Non clogging
5. Blocking and non blocking
6. Synchronous and asynchronous
7. What is? AIO
8. What is? NIO
9. What is? BIO
10. The flow generally does not need to be closed , If it is closed, what method is being used , It's better to close it in that code block , How the process flow is closed , If multiple streams call each other, how does the incoming close ？
11. What is node flow , What is a processing stream , What's the use of each , What are the characteristics of the creation of the process flow ？
12.PrintStream、BufferedWriter、PrintWriter Comparison ?
13. The difference between byte stream and character stream ？
14. How to achieve java serialize ？
15. What is? java serialize ？
16.Java There are several types of flows in ？

3、 ... and 、Java virtual machine

1. How to judge whether a constant is an obsolete constant ？
2. Why program counters are private ?
3.JRE、JDK、JVM And JIT What's the difference between ？
4.JVM What are the tuning commands ？
5. The way JVM Tools for tuning ？
6. Introduce the class file structure ！
7. How to judge a class is useless ?
8.Java Is there a memory leak ？ Please give us a brief description .
9.Minor Gc and Full GC What's the difference ？
10. Let's talk about the basic strategy of allocating objects in heap memory
11. There are several ways to access and locate objects ?
12. The way Java Object creation process
13.Java 8 Why to replace forever (PermGen) Replace with Metaspace (MetaSpace) Well ？
14. Let's talk about the difference between heap and stack
15. How to break the parental delegation model ？
16. Why parent delegation mode is needed ？
17. How to call the route stack information ？
18. Tell me about some of the main JVM Parameters
19. What is? happen-before principle ？
20. What is memory barrier ？
21. What is instruction reordering ？
22.JVM Once complete GC How is the process , How to promote the object to the old age ？
23.JVM Why is the new generation divided into Eden and Survivor？
24. When will stack memory overflow occur ？
25.Java Do you know the layout of objects ？
26.Tomcat How to break the parental delegation mechanism ？
27. What is parental delegation mechanism ？
28. Tell me about the class loaders ？
29. Talk about the process of class loading
30.ZGC What's the use of coloring pointers in collectors ？
31. say something ZGC How the garbage collector works
32. say something G1 How the garbage collector works
33. say something CMS How the garbage collector works
34. What garbage collectors do you know ？
35. Are the objects given priority to the younger generation ？
36.GC Roots What are they? ？
37.JVM How to judge whether an object is to be recycled ？
38.Java What reference types are there in ？
39. What garbage collection algorithms are you familiar with ？
40. Where are string constants stored ？
41. What does the program counter do ？
42. What does the stack frame contain ？

Four 、Kafka 

1. sketch Follower The complete process of replica message synchronization
2.JavaConsumer Why use one-way to get messages ?
3.Controller Network partition occurs (NetworkPartitioning) when ,Kafka What will happen? ?
4.Kafka In which scenarios are zero copies used (ZeroCopy)?
5. Partition Leader There are several election strategies ?
6.consumer_offsets What is it for ?
7.Kafka Can I delete messages manually ?
8.LEO、LSO、AR、ISR、HW What do they mean ?
9.Leader Always -1, How to deal with it ?
10. How to estimate Kafka The number of machines in the cluster ?
11.Broker Of HeapSize How to set up ？
12. monitor Kafka What are the frameworks of ?
13. How to set up Kafka The maximum message size that can be received ?
14. Elaborate Kafka Leader copy in (LeaderReplica) And followers copy (FollowerReplica) The difference between
15. Explain Kafka Medium displacement (offset) The role of
16. What is a consumer group ?
17.kafka How to implement delay queue ？
18.Kafka How does the message order in ？
19. Why? Kafka Read write separation is not supported ？
20.Kafka Whether the message in the will be lost and re consumed ？
21.kafka Of message What's the format like ？
22. If leadercrash when ,ISR What if it's empty ？
23.kafkaunclean What does configuration stand for ？ Would be right sparkstreaming What's the impact of consumption ？
24.kafkaproducer Type data ,ack by 0,1,-1 What do you mean when you're on the road , Set up -1 When , Under what circumstances ,leader Would think of a message commit 了
25.kafkaproducer How to optimize the driving speed ？
26.kafka Why so fast ？
27. Under what circumstances is a broker From ISR Get kicked out of ？
28.kafkafollower How to communicate with leader Synchronous data ？
29.kafka Medium zookeeper What does it do ？ Don't have to zookeeper Well ？
30.kafka Medium broker What is it ？
31.Kafka Medium ISR、AR What does it stand for ？ISR What is the expansion and contraction of ？
32. Why use kafka？ Why use message queuing ？

5、 ... and 、MySQL 

1. explain MySQL External connection 、 The difference between internal connection and self connection
2.Mysql How to optimize DISTINCT?
3. The self increasing primary key is the largest ID Record ,MyISAM and InnoDB How are they stored
4.MySQL Master slave replication principle and process
5.delete、truncate、drop difference
6.key and index The difference between
7.MySQL Optimize
8. Disadvantages of row level locking
9. The advantages of row level locking
10. stay MVCC Concurrency control , What kinds of read operations can be divided into ？
11.MVVC Do you know
12. What's the benefit of table partitioning ？
13. The difference between table partition and sub table
14. What is table partitioning ？
15. Under what circumstances should indexes not be built or less built
16. Let's talk about three paradigms
17. What is stored procedure ？ What are the advantages and disadvantages ？
18. I care about the business system sql Is it time consuming ? Is the statistics too slow ? How to optimize slow queries ?
19. How to deal with large paging ?
20.MySQL Of binlog There are several entry formats ? What's the difference between them ?
21.varchar(10) and int(10) What does it mean ?
22. If you want to store a user's password hash , What fields should be used for storage ?
23. Why do fields need to be defined as notnull?
24. The primary key uses auto increment ID still UUID?
25. Why try to set a primary key ?
26. What happens when an index is created for the column but not used in the query ?
27.MySQL What are the logs , What's the use of each ？
28.MySQL in varchar And char And varchar(50) Medium 50 Meaning of representative
29.MySQL Of redo The timing of log disk brushing
30.MySQL Of redo Journal and undo What's the use of logs ？
31. Why? InnoDB The primary key will be generated ？
32.InnoDB If the primary key is not set , What happens inside it ？
33.InnoDB After deleting a record , What will be done internally ？
34.InnoDB Differences in data storage between primary key indexes and non primary key indexes
35.InnoDB How is your data stored ？
36.MyIsam How is your data stored ？
37.InnoDB Is there a clustered index ？MyIsam Well ？
38. What is a clustered index ？
39.MySQL Type of index
40. I know “ Back to the table ” The concept of ？ Under what circumstances “ Back to the table ”？
41. Do you know the isolation level of transactions ？
42. Talk about what is business ACID Attribute
43. What storage engines have you learned ？ What are the advantages and disadvantages of each ？
44. When building an index , What are the factors to consider ?
45.Hash Index and B+ What are the differences or advantages and disadvantages of tree indexes ?
46. What kind of data structure is index ?
47. What is index ?

8、 ... and 、Netty

1.Netty What are the aspects of high performance ？
2. say something Netty The implementation process of ？
3.Netty Which heartbeat type settings are supported ？
4.Netty There are several ways to send messages ？
5.Netty What are the important components of ？
6.Netty Do you understand the heartbeat mechanism of ？
7.Netty Zero copy of, you know ？
8.Netty Do you know the application scenario of ？
9. Why use Netty？
10.Netty What is it? ？
11.UDP Will the agreement have the problem of sticking and unpacking ？ Why? ？
12. Have you ever learned about sticking and unpacking ？ Why does sticking and unpacking occur ？ How to deal with sticking and unpacking ？
13. What is? Reactor Model ？Reactor Of 3 Do you know both versions ？

  Nine 、RabbitMQ

1.vhost What is it? ？ What's the effect ？
2.RabbitMQ There are several types of broadcasts ?
3. What are the conditions for successful message persistence ?
4. How to ensure that messages are sent to RabbitMQ? How to ensure that the message receiver consumes the message ?
5.RabbitMQ What are the important roles ?
6.RabbitMQ What are the use scenarios of ?
7.RabbitMQ How to avoid message loss ？
8.RabbitMQ How are the messages sent ？
9. if cluster Have one of queue Of owner node It doesn't work , And the queue Be declared to have durable attribute , Whether it can succeed from other node On redeclaration of the queue ？
10. The client connects to cluster Any of the node Is it all working ？
11. In the single node System and multi node Composed of cluster The system states queue、exchange, And binding What would be different ？
12. What is metadata ？ What are the types of metadata ？ What is included ？ And cluster Related metadata some ？ How metadata is stored ？ Metadata is in cluster How is it distributed in ？
13.RabbitMQ What are the advantages and disadvantages ？
14. What is? RabbitMQ？ Why use RabbitMQ？
15. The use of dead letter queue and delay queue
16. How to avoid repeated delivery or consumption of messages ？
17. How to ensure that the message receiver consumes the message ？
18. How to route messages ？
19. How messages are distributed ？
20. What transmission is the message based on ？

  Ten 、Redis

1.Redis How to optimize memory ？
2.Redis What's the use of the pipe in ？
3.Redis and Redisson What does it matter ？
4.Redis What are the suitable scenes ？
5.MySQL Are there in 2000w data ,redis The only known 20w The data of , How to ensure redis The data in It's hot data ？
6.Redis When will the cluster scheme cause the whole cluster to be unavailable ？
7.Redis What should the cluster solution do ？ What are the plans ？
8.Redis String What are the internal codes of ？
9. use Redis Delay queue , How to realize ？
10.Redis Find in the cluster key When , How to locate specific nodes ？
11.Redis Have you ever known about persistence ？
12.Redis When will it be triggered key The recycling of ？
13.Redis key What are the elimination strategies ？
14.Redis Have you understood the transaction mechanism ？
15. Use Redis Statistics website of UV, What to do ？
16.Redis The big of the middle key How to deal with ？
17.Redis The heat in key How to deal with ？
18. Cache invalidation ？ Cache penetration ？ Cache avalanche ？ Cache concurrency ？
19.Redis How do clusters choose databases ？
20.Redis How to set password and verify password ？
21. Why? Redis You need to put all the data in memory ？
22.Redis Why doesn't the government provide Windows edition ？
23.Redis Single thread or multi thread ？
24.Redis Why so fast ？
25. What is the maximum storage capacity of a string type value ？
26.Redis What is the full name of ？
27.Redis What are the main physical resources consumed ？
28.Redis What are the data structures ？
29.Redis comparison memcached What are the advantages ？
30. What is? Redis？ Briefly describe its advantages and disadvantages ？

11、 ... and 、Spring

[email protected] and @Bean What's the difference ？
2.Spring What design patterns are used in the framework ？
3.Spring MVC You know how it works ？
4.Spring Medium bean Have you learned about the life cycle ？
5.Bean Factories and Application contexts What's the difference? ？
6.ApplicationContext What is the usual implementation ?
7.Spring AOP Realization principle
8. What are the different types IOC( Dependency injection )？
9. Explain the various modes of automatic assembly ？
10.Resource How to be found 、 Loaded ？
11.BeanFactory and ApplicationContext What's the difference? ？
12.Spring The underlying principle of transaction
13.Spring What are the transaction propagation behaviors in a transaction ？
14.Spring What are the isolation levels in a transaction ？
15.Spring There are several ways to manage transactions ？
16. Declare a class as Spring Of bean What are the annotations for ？
17.Spring Single case in bean Do you understand the thread safety of ？
18.Spring Medium bean What are the scope of ？
19. Talk about yourself about Spring AOP The understanding of the
20.Spring AOP and AspectJ AOP What's the difference? ？
21. Talk about yourself about Spring IOC The understanding of the
22.Spring Boot There are several ways of manual assembly ？
23.Spring How to solve the circular dependence ？
24.Spring Which modules are composed of ?
25. Use Spring What are the benefits of a framework ？
26. What is? spring?

  Twelve 、Spring Boot

1.SpringBoot 2.X What's new ？ And 1.X What's the difference? ？
2. Protect SpringBoot What are the methods of application ？
3.Spring Boot What are the core annotations ？ Which annotations does he consist of ？
4.Spring Boot How to solve cross domain problems in ？
5. Compare the Spring Security and Shiro Advantages and disadvantages of each ？
6. How to achieve Spring Boot Application security ？
7. What is? Swagger？ Do you use Spring Boot Has it come true ？
8. How to use the configuration file through Spring Boot Configure the configuration of a specific environment ？
9. How to use Spring Boot Deploy to different servers ？
10. How to be in Spring Boot Add generic JS Code ？
11. What is embedded server ？ Why do we use embedded servers ?
12. Why do we need spring-boot-maven-plugin?
13.Spring Initializr Is to create Spring Boot Projects The only way ？
14. How do you use it? Maven To build a SpringBoot Program ？
15. How to be in Spring Boot disable Actuator Endpoint security ？
16.Spring Boot What is the monitor in ？
17. How to reload Spring Boot Changes on , Without restarting the server ？
18.Spring and SpringBoot What's the difference ？
19. Create a Spring Boot Project What is the easiest way ？
20.Spring Boot What are the advantages ？
21. What is? springboot

13、 ... and 、Spring Cloud

1.Eureka and zookeeper Can provide service registration and discovery functions , The difference between the two
2.SpringCloud Config Can you refresh in real time ?
3. What is? Spring Cloud Bus?
4. How to realize dynamic Zuul Gateway route forwarding ？
5.ZuulFilter What are the common methods ？
6. What is the avalanche of services ?
7. What is service fusing ？ What is service degradation ？
8. What is? zuul?
9. say something Eureka Self-protection mechanism ？
10.Eureka How it works ？
11. What is? Netflix Feign？ What are its advantages ？
12. What is? Hystrix Circuit breaker ？ Do we need it ？
13. What is? Hystrix？ How does it achieve fault tolerance ？
14.Spring Cloud Which components are made up of ？
15. What does service registration and discovery mean ？Spring Cloud How to achieve ？
16. Use Spring Cloud What are the advantages ？
17. What is? Spring Cloud？

fourteen 、Zookeeper

1.zookeeper Load balancing and nginx Load balancing difference
2.Zookeeper and Dubbo The relationship between ？
3.Zookeeper Typical application scenarios
4.ZAB and Paxos The relation and difference of algorithm ？
5.Zookeeper For nodes watch Are monitoring notifications permanent ？ Why not forever ?
6. Does the cluster support dynamic addition of machines ？
7. Cluster at least a few machines , What are the rules of clustering ?
8.Zookeeper What are the deployment modes ？
9.zk How are node outages handled ？
10. Why do distributed clusters have Master？
11.zookeeper How to ensure the order consistency of transactions ？
12. Data synchronization
13.Zookeeper Next Server Working state
14. Server role
15.ACL Authority control mechanism
16. Server-side processing Watcher Realization
17. Client registration Watcher Realization
18.Zookeeper Watcher Mechanism
19.Zookeeper file system
20.ZooKeeper What is offered ？
21.ZooKeeper What is it? ？
22.Zookeeper How to implement service registration ？
23.Zookeeper Leader What is the election process ？
24.Zookeeper How to ensure data consistency ？
25.Zookeeper How to implement distributed locks ？
26. Read about Zookeeper Of ZAB Agreement ？
27.Zookeeper What are the node types ？

  15、 ... and 、 Multithreading

1. How will you use thread dump？ How will you analyze Thread dump？
2. stay Java in Lock Interface than synchronized What are the advantages of block ？ You need to implement an efficient cache , It allows multiple users to read , But only one user is allowed to write , In order to maintain its integrity , How will you achieve it ？
3. High concurrency 、 How to use thread pool for business with short task execution time ？ Low concurrency 、 Business with long task execution time How to use thread pool ？ High concurrency 、 How to use thread pool for long running business ？
4. Synchronization method and synchronization block , Which is the better choice ？
5.Hashtable Of size() There is only one statement in the method ”return count”, Why do I have to synchronize ？
6.Semaphore What's the role ？
7. Thread security in singleton mode
8.Java What is the thread scheduling algorithm used in ？
9.Java How to get the thread dump file
10. What is thread safety ？
11. What kinds of work queues do thread pools have ？
12. Talk about several common thread pools and applicable scenarios ？
13.synchronized Key words and volatile The difference between keywords
14. What is the thread blocking problem ？ How to solve ？
15. What is the thread starvation problem ？ How to solve ？
16. What is a live lock ？
17. What is thread safety ？ How to solve ？
18. Why we call start() Method run() Method , Why can't we call it directly run() Method ？
19. What is thread deadlock ? How to avoid deadlock ?
20. The difference between concurrency and parallelism ？
21. Why virtual machine stack and local method stack are private ?
22. Why program counters are private ?
23. What are threads and processes ?
24. What is multithreaded context switching ？
25. What is spin lock ？
26.AQS Several synchronization modes are supported ？
27. What is? AQS？
28.CAS The problem of
29. What is? CAS？
30.CyclicBarrier and CountDownLatch The difference between
31. Advantages of thread pool ？
32. How to create threads ？
33. Three elements of concurrent programming ？
34. What is a pessimistic lock ？ What is an optimistic lock ？
35.Java What is the status of the thread in ？
36. How to avoid “ False sharing ”？
37.“ False sharing ” What are the reasons for this ？
38. Know what is “ False sharing ” Do you ？
39. The way synchronized Lock upgrade process
40.ReentrantLock And synchronized The difference between
41. say something synchronized Implementation principle of
42.sleep() Methods and wait() The differences and similarities of methods ?
43.Thread.sleep(0) What is the role of ？

sixteen 、 Distributed  

1.SOA What are the differences between microservice architecture and microservice architecture ?
2.BASE Did you understand the theory ？
3. How to guarantee the order of request execution
4. Interface idempotent design of distributed system
5. How to design a seckill system ?
6. How to prevent form from submitting repeatedly ？
7. Distributed Session Do you know ？ How to achieve ？
8. The difference between forward agent and reverse agent
9. What are the implementation schemes of load balancing ？
10. What load balancing algorithms have you learned ？
11.TCC Do you know ？
12. What is phase two submission （2PC）？ What is a three-stage submission （3PC）？
13. Have you learned about distributed transactions ？
14. What is? CAP Theorem ？
15. Do you know the snowflake algorithm ？

seventeen 、 computer network

1.HTTP What requests does the agreement include ？
2. Enter... In the browser url The process from address to display home page
3. Congestion control
4. Sliding window and flow control
5.TCP Why wave four times
6.TCP Why should I return... When establishing a connection SYN
7. Why? TCP Three handshakes
8. say TCP Three handshakes of
9. sketch ICMP、TFTP、HTTP、NAT、DHCP agreement
10. sketch ARP How the address resolution protocol works
11. sketch IP Classification of addresses ?
12. say TCP、IP Four layer model
13. Can you say OSI Seven layer model ?
14. What private （ Retain ） Address ？
15.TCP Corresponding agreement and UDP Corresponding agreement
16. Please briefly TCP and UDP The difference between

  eighteen 、 Design patterns

1.Spring Which design patterns are used ？
2.Dubbo What design patterns are used in the source code ？
3. Give me an example , In this case, you are more likely to use abstract classes , Not the interface ？
4. The difference between the factory pattern and the abstract factory pattern ？
5. Give me an example of a design pattern that conforms to the principle of opening and closing ？
6.OOP The combination of 、 What's the difference between aggregation and Association ？
7. What's the difference between adapter mode and proxy mode ？
8. What's the difference between adapter mode and decorator mode ？
9. What is the adapter mode ？ When to use ？
10. Briefly describe what you know Java Design patterns （ summary ）
11. Talk about what you are familiar with or have heard of j2ee Several common patterns in ?
12. The type of design pattern
13.Java How to implement singleton mode ？
14. Six principles of design pattern ？
15. What is the interface ？ Why use interfaces instead of concrete classes ？

nineteen 、 Data structure and algorithm

1. To talk about ,id Globally unique and self increasing , How to achieve ？
2. What is? B+ Trees ?
3. What is? B Trees ?
4. Why design suffix expressions , What are the benefits ？
5. Please tell me about LRU The implementation principle of the algorithm ？
6. How to 1 To 100 Missing number found in integer array of ?
7. Two point search, understand ？
8. The difference between arrays and linked lists
9. Introduce to you , What is the principle of heap sorting ？
10. How to know the depth of a binary tree ？
11.TreeMap and TreeSet How to compare elements in sorting ？Collections In a tool class sort() How to Compare elements ？
12. What is algorithm ？

twenty 、 Microservices

1. As a service registry ,Eureka Than Zookeeper Fortunately, where ?
2.Eureka What is the basic structure of ？
3. What is? Eureka Service registration and discovery ？
4. What do you know about the microservice technology stack ？
5. What is service fusing , What is service degradation
6. Please talk about right SpringBoot and SpringCloud The understanding of the
7. How micro services communicate with each other ？
8. What is microservice ？
9.Spring Cloud and dubbo The difference between ?
10. What does service registration and discovery mean ？Spring Cloud How to achieve ？
11.Spring Cloud What problems have been solved ？
12. monolithic ,SOA What's the difference with microservice architecture ？
13. What are the characteristics of microservices ？
14. What are the advantages and disadvantages of microservices ？

The 21st 、 Message queue

1. Why use message queuing ？
2. How to solve the problem of message queue delay and expiration ？ What to do when the message queue is full ？ There are millions of How to solve the backlog of messages for several hours ？
3. Various MQ Comparison
4. What about message queue backlog
5. How messages guarantee idempotency
6.Kafka Is the news of the order ？ If you promise Kafka The order of the message ？
7. Using message queuing , If handling duplicate messages ？
8. Using message queuing , How to ensure that messages are not lost ？
9. What are the disadvantages of message queuing ？
10. What are the application scenarios of message queuing ？

twenty-five 、Java8

1.Lambda The argument list of the expression is the same as Lambda What's the difference between arrow operators ？
2. What makes JavaSE8 Better than the others ？
3. What is? Java8 Medium MetaSpace？ It is associated with PermGen Space What's the difference? ？
4.Lambda The advantages of functions
5. What is? Lambda expression ？
6. explain Java8 Intermediate operation and terminal operation ？
7.hashMap principle ,java8 Changes made
8.Java8 What are the options in ？
9.Java8 What does it mean to support functional programming ？
10. Similarities and differences between abstract classes and interfaces ？
11.Java 8 Introduction to new features

hexacosa- 、Java High concurrency

1.ForkJoin frame
2.Java The blocking line in
3.AQS
4.CopyOnWriteArrayList
5.Nginx How to realize high concurrency in multi process model ？
6. Common synchronization tool class ？
7. Common concurrent containers ？
8. Deadlock avoidance and diagnosis ？
9. What is lock sequence deadlock ？
10. Database deadlock ？
11. What is a thread scheduler (Thread Scheduler) And time (Time Slicing)？
12. There are three threads T1,T2,T3, How to ensure that they are executed in order ？
13. How to test concurrency ？
14.Java in Unsafe Class explanation
15. Process scheduling algorithm
16. What's the difference between synchronous and asynchronous , When to use them separately ？ Illustrate with examples
17. How threads communicate
18. How to communicate between processes
19. What is thread
20. What is a process

  twenty-seven 、Java aggregate

1.Iterator What is it? ？
2. why Map Interface non-inheritance Collection Interface ？
3. why Collection Not from Cloneable and Serializable Interface inheritance ？
4. What are the advantages of generics in a collection framework ？
5.Java What is a collection framework ？ Name some of the advantages of the collection framework ？
6. Talk about right HashMap Initial capacity in construction method 、 Understanding of loading factors
7.HashMap What is the default initialization length ？
8.ArrayList and LinkedList The difference between ？
9.ArrayList and Vector The difference between ？
10.ConcurrentHashMap Realization principle
11.ConcurrentHashMap and Hashtable The difference between ？
12.HashMap And HashTable The difference between ？
13. Common collection underlying implementations
14. What are the common collections ？
15.Comparable and Comparator What's the difference between interfaces ？
16.Collections What is the class ？
17. What are queues and stacks , List their differences ？
18.BlockingQueue What is it? ？
19. Which collection classes provide random access to elements ？
20. How to choose HashMap still TreeMap？
21. Can we use any class as Map Of key？
22.hashCode() and equals() How important is the method ？
23.fail-fast And fail-safe What's the difference? ？
24.Iterater and ListIterator What's the difference between ？
25.Enumeration and Iterator Interface differences ？

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