From disheartened to self-study Java 3 months to get the offer, thanks to this document

Job hopping happens all the time, but I suggest that you think about why you want to change jobs before you change jobs. Don't follow the trend. Seeing colleagues leave one by one, I started interviewing blindly (didn't prepare well during the period). Is it because of technical reasons (affecting my own development, deviating from my planned trajectory), or money? Less, less attention.

Elaborately summarize the difficulties of the interview, I hope you can help me

01- Java basic interview questions

The difference between List and Set
How HashSet is guaranteed not to be duplicated
Is HashMap thread-safe, why is it not thread-safe (it is best to draw a picture to show that it is not safe in a multi-threaded environment)?
The difference between HashMap 1.7 and 1.8, what optimizations did 1.8 do, and how?
final finally finalize
Strong references, soft references, weak references, phantom references
java reflection
Arrays.sort implementation principle and Collection implementation principle
Application of LinkedHashMap
Implementation principle of cloneable interface
Exception classification and handling mechanism
The difference between wait and sleep
.........

Q.1-Basic link interview skills, answers to interview questions!

The main points of investigation:

JAVA Exception Classification and Handling
javareflection
JAVA annotations
JAVA inner class
Java Generics
JAVA serialization (creating reusable Java objects)
JAVA copy

02-Java concurrency

Synchronized implementation principle and lock optimization?
The realization principle of volatile?
Semaphores for Java?
What is the difference between synchronized in static method and normal method?
How to realize that all threads wait for an event to execute before they execute?
CAS? What's wrong with CAS and how can it be fixed?
What is the difference between synchronized and lock?
How is Hashtable locked?
Concurrency issue with HashMap?
Introduction to ConcurrenHashMap? Why use red-black tree in 1.8?
AQS
How to detect deadlock? How to prevent deadlock?
Java memory model?
How to ensure the correct result of i++ under multithreading?
Types, differences and usage scenarios of thread pools?
Analyze the implementation principle of the thread pool and the thread scheduling process?
How to tune the thread pool and how to confirm the maximum number?
The principle of ThreadLocal, what should be paid attention to when using it
The usage of CountDownLatch and CyclicBarrier, and the difference between them?
LockSupportTools
Condition interface and its implementation principle
Understanding of the Fork/Join framework
The principle of segmented lock, the thinking of reducing the lock force
Eight kinds of blocking queues and the characteristics of each blocking queue
.........

Q2-Multi-threaded concurrency needs to master knowledge points and answers to interview questions

JAVA blocking queue principle
Usage of Cycli cBarri er, CountDownLatch, Semaphor e
The role of the volatile keyword (variable visibility, reordering prohibited)
How to share data between two threads
ThreadLocal role (thread local storage)
The difference between synchro oni red and Reentr antLock
Concurr entHashMlap concurrent
Thread scheduling used in Javs
Process Scheduling Algorithm
What is CAS (compare and exchange optimistic locking mechanism lock spin)
What is AQS (Abstract Queue Synchronizer)

03- Spring

BeanFactory 和 FactoryBean
Understanding of Spring IOC, 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 guarantee the security of Controller concurrency?
........

Q3, spring interview core and analysis of the principles behind the interview questions

Mainly master the following aspects:

Principle of Spring I0C
Principle of Spring APO
Principles of Spring MVC
Principles of Spring Boot

04-Distributed + lock related

The underlying implementation principles and mechanisms of Dubbo
Describe the detailed process of a service from publishing to being consumed
How to do service governance in distributed systems
The concept of idempotence for interfaces
How does message middleware solve 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 implement load balancing, and what algorithms can be implemented?
What is the purpose of Zookeeper and the principle of election?
Vertical split of data and horizontal split.
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, and what are the advantages and disadvantages compared with other MQs? Is the MQ connection thread-safe?
How to ensure that the data of the MQ system will not be 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
......

Distributed core:

distributed transaction
distributed cache
distributed lock

05-database

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

Q5, database interview topic and answer analysis

06-Redis

What data data has been used by Redis, and how to implement the bottom layer of Redis
Redis cache penetration, cache avalanche
How to use Redis to implement distributed locks
How to solve the concurrent competition problem of Redis
Several ways of Redis persistence, what are the advantages and disadvantages, and how to achieve it
Cache invalidation strategy for Redis
Redis cluster, high availability, principle
Redis cache fragmentation, Redis data elimination strategy
.....

Redis interview essence document

Redis interview essence document

Prepare before the interview, be prepared, you can read more interview questions, look at the needs of the recruiter, and learn more about the market