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Even liver three all night, jvm77 high frequency interview questions detailed analysis, this?

2020-11-06 01:39:00 【Procedural ape space】

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Preface

After the painful spring and autumn moves , I've also accumulated some facial scriptures , I hope it can help you . Due to the word limit, those who need answers can pay attention to GZH【 Programmer space 】 Get the full version free of charge PDF

other

What 什 Is idempotent ？ What 什 In this case, we need to consider idempotent ？ How do you solve the idempotent problem ？

Java

Multiple threads read and write at the same time , Number of read threads 量 Far away ⼤ Larger than the writing thread , How do you think it should be solved Concurrent problems ？ You'll choose gash 什 What kind of lock ？
JAVA Of AQS Yes No 了 Explain , It is ⼲ What do you do? ？
except 了synchronized Besides keywords , How do you ensure thread safety ？
What 什 When do you need to add volatile keyword ？ Does it guarantee thread safety ？
If all threads in the thread pool are busy , Submit ⼀ A new mission , Will send ⽣ What's the matter 什 Well ？ queue 列 All stuffed 了 after , Still busy , Submit again and send ⽣ What's the matter 什 Well ？
Tomcat Your own parameters ⼀ How do you usually adjust ？
synchronized What's locked in by keywords 什 Modong ⻄ In the west ？ How is it represented in bytecode ？ , What is the representation of the object in existence 什 Well ？
wait/notify/notifyAll⽅ The method needs not 不 Need to be included in synchronized In block ？ Why is this 什 Well ？
ExecutorService you ⼀ How do you usually ⽤ With ？ Is each service discharge ⼀ One is still ⼀ One item ⽬ Objective ⾥ in 里⾯ Put ⼀ One ？ What do you have 什 What's the benefit ？ Spring
Do you have ⽤ Used to Spring Of AOP? yes ⽤ be used for ⼲ What do you do? ? ⼤ How to make ⽤ use ？
If ⼀ One by one ⼝ Oral 2 No 不 The realization of the same , So how to come to Autowire⼀ A specified implementation ？
Spring Declarative transactions @Transaction annotation ⼀ It is usually written in what 什 What position? ? Throw out 了 abnormal Meeting ⾃ Auto roll back ？ Is there any way to control it 不 Trigger rollback ?
If you want to be in a Bean⽣ After generating and assembling, execute ⾏ That's ok 行⾃ since ⼰ My own logic , What can be 什 Well ⽅ The way is present ？
SpringBoot Didn't put it in web Containers 器⾥ in 里 Why? 什 You can't run HTTP service ？
SpringBoot If you want to make ⽤ use ⾃ Custom configuration ⽂ file ⽽ Instead of 不 just application.properties, What should I do 弄？
SpringMVC in RequestMapping You can specify GET, POST⽅ Methods? ？ How to designate ？
SpringMVC If you want to output Object( example 例 Such as XXResult perhaps XXResponse) this The packing is JSON Output , What to do with 理?
How to intercept SpringMVC It's abnormal , Then I do ⾃ Custom processing 理,⽐ For example, fight ⽇ Journal or packaging become JSON

MySQL

If there's a lot of data to plug in ⼊ Enter into MYSQL What would you choose 什 Well ⽅ The way ?
If the query is slow , You will think of the ⼀ One ⽅ What is the way 什 Well ？ The index is ⼲ What do you do? ?
If it's built 了⼀ A single column 列 Indexes , Find out 2 Column 列, Meeting ⽤ Use this single column 列 Index ？
If it's built 了⼀ One contains more than one column 列 The index of , When you look up, it's just ⽤ It was used 了 The first ⼀ A column of 列, Can't you 不 can ⽤ use This index ？ Look up three columns 列 Well ？
Pick up the question , If where After the condition ⾯ There is ⼀ One i + 5 < 100 Can make ⽤ Use this index ？
How to see if ⽤ Yes 了 Some index ？
like %aaa% Can make ⽤ Use the index ? like aaa% Well ?
drop、 truncate、 delete The difference between ？
How do you usually monitor the database ? slow SQL How to check ？
Is your database ⽀ Support emoji expression , If you don't 不⽀ Support , How to operate ?
The amount of data in a single table in your database 量 How much is the ？⼀ In general, there are many ⼤ When you are big, query performance is urgent Dramatic decline ？
The inquiry is dead 了, I want to find out ⾏ That's ok 行 The query process of ⽤ What to use 什 You order ？ After finding out ⼀ Generally you Meeting ⼲ why ？
How is the separation of reading and writing done ？ What do you think middleware will do ？ This operation has something to do with affairs What 什 What's the matter ？
Has the sub database and sub table been made ？ What is the online migration process like ？ How to make sure the data is positive Yes ？

JVM

What do you know or do you use online ⽤ What to use 什 Well GC Strategy 略? What does it have 什 What's the advantage , optimum ⽤ For what 什 Well scene ？
JAVA Class loader 器 Include ⼏ several ？ Between them ⽗ Father ⼦ What's the relationship like ？ Parents' appointment machine What is the system 什 What do you mean ？ What do you have 什 What's the benefit ？
how ⾃ Customize ⼀ A classloader 器？ You make ⽤ What have you used or what you are 什 You need to ⼀ One ⾃ since Defined class loaders 器 Do you ？
What are the parameters of heap memory setting 什 Well ？
Perm Space What's in it 什 Data ? Can cause OutOfMemory Do you ？
do gc when ,⼀ An object in the memory of each Space What's the order of being moved in 什 Well ？
Have you ever met OutOfMemory problem ？ How do you deal with 理 Of this question ？ Handle 理 What's in the process ？
1.8 after Perm Space What are the changes ? MetaSpace⼤ Big ⼩ The little default is ⽆ Infinite ? still What will you pass 什 Well ⽅ The way to specify ⼤ Big ⼩ Small ?
Jstack yes ⼲ What's going on 什 Well ? Jstat Well ? If online programs periodically get stuck , You suspect that Can be gc As a result of , How would you investigate this problem ？ Threads ⽇ journal ⼀ You usually look at what's in it 什 Well part ？
StackOverFlow Have you ever encountered an exception ？⼀ You usually guess what it will be 什 Under the circumstances of being touched Hair ？ How to specify ⼀ A thread stack ⼤ Big ⼩ Small ？⼀ How much do you usually write ？

Linux command

0. add to Java Study ：1037935907

⽇ The journal is special ⼤ Big just wants to see the last 100⾏ That's ok 行 How to get 弄? If you want to ⼀ Keep watching ⽇ Continuous output of logs ,⽤ use What 什 You order ?
If ⽇ journal ⼀ Output ,⼀ At the same time, I want to see if there is a keyword and how to do it in real time 弄？
grep If you ignore 略⼤ Big ⼩ How to make lowercase 弄? Regular expressions ？
vim Down ⼀ One ⾏ That's ok 行 What is it 什 Mo key ？ Down 30⾏ That's ok 行 Well ? Jump to the ⽂ end of file ⼀ One ⾏ That's ok 行 What is it 什 Well ? Jump back What is it 什 Well ? What is the backward search 什 Well ?
If there is one ⽂ Text ⽂ file , Use spaces as columns 列 The delimiter , If you want to count the third column 列⾥ in 里⾯ Every face How to deal with the number of occurrences of a word 弄？
If you put it on ⾯ How to arrange the number of times the face appears 弄? Want to follow the order of the numbers themselves ⽽ Instead of 不 yes character string 串 The order of 列 How to get 弄？
Linux environment variable 量 Why 什 As a separator ？ environment variable 量 Through what 什 Command settings ？
To someone ⽂ Document rights are limited ⽐ For example, set to 644 yes ⽤ What to use 什 You order ？ This 6 What is it 什 What do you mean ？
Linux Next ⾯ If you want to see the resources occupied by a process ⽤ What's the use situation ？ System load⼤ Probably What do you mean 什 What do you mean ？ Your online system load⼀ Generally how much ？ If ⼀ One 4 Nuclear machine 器, You think more Less load yes ⽐ More normal ？ top command ⾥ in 里⾯ Face to face ⼀ once 1 Will send ⽣ What's the matter 什 Well ?
top command ⾥ in 里⾯ Noodles , Sometimes all the processes CPU send ⽤ The usage rate adds up to more than 100% How to get back to things ？
What other commands are available to check system performance or find problems ？ you ⼀ It's usually to see which ginseng Count ？
Want to see a process open 了 Which? ⽹ What is network connection 什 You order ？⾥ in 里⾯ The state of face connection you ⽐ Compare Turn off ⼼ My heart ⼏ several ？

-- Partial topic

Have you ever done Linux system parameter ⽅ Fang ⾯ Face optimization ,⼤ Maybe what has been optimized 什 Well ？
system parameter ⾥ in 里⾯ There's a noodle called backlog Can ⽤ be used for ⼲ What's going on 什 Well ？
see ⽹ Network connection found a lot of TIME_WAIT It could be something 什 Why ？ Your answer is ⽤ What's the use of it 什 Yao impact ？ What would you choose 什 What kind of ⽅ To reduce these TIME_WAIT
May I introduce ⼀ once TCP Three grip ⼿ The process of the hand , If there's a ⽹ Network program , you ⽤ Use the third ⽅ Fang Of library To send data , You suspect this library There's something wrong with the data sent , So how to test Prove ？ tcpdump Derived ⽂ File you ⼀ How to analyze it in general ？
KeepAlive yes ⽤ be used for ⼲ What's going on 什 Well ？ What's the advantage of this 什 Well ？

Redis

-- Development

Cache penetration can introduce ⼀ For a second ？ How do you think this problem should be solved
How do you trigger caching more 更 new ？ (⽐ For example, set the timeout time ( passive ⽅ The way ), ⽐ For example, more 更 The new time Wait for the initiative update)？ If it's passive ⽅ How to control multiple ⼊ Enter into ⼝ At the same time, the port triggers a cache change 更 new ？
You ⽤ use Redis What to do 什 Well ？ Why? 什 Well, No 不⽤ Use something else KV Storage example 例 Such as Memcached, Cassandra etc. ?
You ⽤ What to use 什 Well Redis client ? Redis⾼ Reasons for high performance ⼤ It can be said that ⼀ some ?
What are you familiar with Redis Data structure of ? zset yes ⼲ What's going on 什 Well ? and set What do you have 什 What's the difference ?
Redis Of hash, What is the specific command to store and retrieve 什 What's the name ?
LPOP and BLPOP The difference between ?
Redis There are ⼀ Some contain SCAN The command for the keyword is ⼲ What do you do? ? SCAN The amount of data returned 量 yes Fixed ?
Redis Medium Lua Did you make ⽤ Used to ? Sure ⽤ What is it for 什 Well ? Why? 什 You can do this ⽤ use ?
Redis Of Pipeline yes ⽤ be used for ⼲ What's going on 什 Well ?

-- Operation and maintenance

Redis Persistence ⼤ There are about ⼏ several ⽅ The way ? aof and rdb What's the difference 什 Well ? AOF What do you have 什 What are the advantages and disadvantages Would you like some ?
Redis Replication Of ⼤ What is the general process 什 Well ? bgsave The execution of this order ⾏ That's ok 行 The process ? -- Partial topic
If there are many KV Data to be stored in Redis, But memory is not 不⾜ foot , Through what 什 Well ⽅ The way can be contracted Reduce memory ? Why? 什 Well, it can shrink ⼩ Small memory ?
Redis in List, HashTable all ⽤ Yes 了ZipList, Why? 什 Will you choose it ? monitor 、 stability
Business ⽇ What is the log through 什 Well ⽅ Way to collect ？
Online machine 器 How to monitor ？ Mining ⽤ What to use 什 Open source products or ⾃ Self developed products ？ It's a minute level It's in seconds ？
If you can find a way to collect ⼀ One JAVA The back end should ⽤ Performance data used , What do you care about ⽅ Fang ⾯ Noodles ? What would you choose 什 What kind of ⼯ Tools 、 Ideas 路 To collect ?
⼀ You usually tune ⽤ Use the third ⽅ Fang will not 不 Can monitor the tune ⽤ Use situation ？