Interview summary——Java Skills a senior engineer should master

I also summed up one and two before the interview, This third part may be more inclined to the inner monologue and the summary of interview skills.....

One, monologue


I interviewed people before, Now it's your turn to find a job, How to put it? Every interviewer's opinion is different, The way of interview is different, For example, when I interview people, I like to ask about the projects he uses, Then ask some questions about the technology used, Or I like to ask about some technical solutions for some scenarios, For example, when your interface service data is intercepted, How do you prevent data from being submitted maliciously?
relatively speaking,Java The bottom and foundation of, Of course, asking less doesn't mean not asking, It's about your projects and your design ideas. Of course, Know the basics and the bottom better, This will let you know, Know why, The written code and program are more robust and maintainable. So, The foundation is still very important.


Now it's your turn to go out for an interview, How to put it? Actually, I'm nervous, I thought I would not be nervous or anxious, Actually, Yes, there are. When you don't find the right job, I can't even sleep at night, I always feel that something is on my mind, I don't feel comfortable sleeping. Since I can't sleep, Let's look at the information, I have a habit, Some problems before going to bed, The next morning, I can think of the answer, Take notes before going to bed, The next morning, I can remember it very deeply, No more bullshit, Go straight to the point.

Two, Interview skills

1, Memorize your resume


Reason: First question of interview, It's usually about introducing yourself, Or introduce your recent project, And an interviewer, If you don't know your resume well, For the items mentioned in it, If technology can't be described clearly, I don't think any company will accept this, Even if you are a super talent, You can't express yourself, I guess it's a headache, therefore, Bear in mind: Be sure to recite your resume, You don't have to write it all down, At least remember the two companies you've been with recently, The projects you have done in these two companies, Module you are responsible for, The technology used in the project and the corresponding technical implementation scheme( This is especially important).

2, In depth understanding and memorizationJava Basic knowledge


Reason: Most companies interview junior or senior, Whether it's a written test or an interview, They will ask a series of basic questions, These basic questions includejvm, Character string, aggregate, Threads, etc. You can't remember every one of them, So it's memory in understanding, takejvm Speaking
, If I ask you to talk about your rightjvm Understanding,
So you have to know firstJVM What are the structure components, What does each structure do, Then consider aJava Objects from creation to recycling, How to approachJVM Of these structures. If you synthesize memory from these aspects, Believe in doing more with less, And you understand it better.
As for the meeting, Give an exampleList Set belowArryList,LinkedList,Vector The difference between equal sets, So the same way, You need to understand the structure of each one, You know what he does, So you can use it more succinctly, And during the interview, Not dumb.

3, Maintain self-confidence and a heavy and calm mind

Reason: During the interview, Confidence is indispensable, Believe you can, On the way to the interview, you can say to yourself: I belive I can !
That's what I did anyway, My heart, In fact, when facing the interviewer, Your confidence will also make the interviewer think you are a very confident person, At least I feel like I'll give you a high score. The other thing is to stay calm, If you want to provide a technical solution or talk about a technical principle, There's no need to talk about everything, You can tell the interviewer: Let me think first. And then assemble the knowledge in memory, Language under assembly, Put it in order, So that you can show your talent better, Isn't it??
Everyone will be nervous during the interview, I get nervous, too, Sometimes I forget what I remember, No problem, Boldly forget, Or I don't know.
Remember, Part of it doesn't matter, If you know everything, Then you should beCTO Grade( To make fun of).

4, Try to remember that you can't answer the interview or that there are inappropriate questions


Reason: It doesn't matter if the interview fails, After all, every company has different requirements, The questions you ask may differ from what you are good at, But remember one thing: You can't answer the questions during the interview, Or you feel like you're not answering the right questions, Write it down, If not, You can ask the interviewer on the spot if he has a good answer, If the interviewer doesn't want to tell you( Generally speaking, the interviewer is lazy to answer you), Then you go home and check the data, If it's some specific technology, You can also write your own cases or something, After all, there are so many knowledge points, Problems vary, Principle unchanged, Interview is also a process of learning knowledge, Let you know the technology that most companies need or require at present. I don't know this time, Next time

5, Before the interview, It's better to know about the company you are going to interview( Including products, Project situation)

Reason: It is said that, Know yourself as well as the enemy, You can fight a hundred battles with no danger of defeat, Interview is a battle, You need to know the basic information of your interview company, Including job requirements, In this way, you can roughly know the technical requirements of the company you need to interview.
Why let you know the company's main products and projects, So that you can get a general idea of the technical structure of the company, Including the questions and doubts you may have about one of their implementations, I'm sure the interviewer would like to help you with these questions. So you're trying to show, And learned, Why not.

6, Arrange your interview time reasonably( If there's an interview with more than one company, Try to put the company you want to go to last for an interview)


Reason: I don't think many people understand that, Maybe most people are confused about how to arrange the interview time, Random arrangement. But here's a trick, If there are multiple interview opportunities at the same time, You put your favorite company at the bottom of the interview, So you've gone through the previous corporate screening, If it works, it's an opportunity, If it doesn't work, For the last.
But here are two things to consider:1, You need to remember the company and basic information of your resume( That means you're not from Haitou)
2, If you can't remember, Then you can answer it for a while, After learning about the company, By email or other means, Adjust interview time. It is also suggested that no more than two interviewing companies should be arranged for one day, The best is in the morning, One afternoon, So you have plenty of time to adjust.

Three, Basic summary of interview questions

1, JVM Structural principle,GC Detailed explanation of working mechanism

answer: Specific reference:JVM structure,GC Detailed explanation of working mechanism, Speaking ofGC, Remember two points.:1,GC It is responsible for reclaiming the memory space of all objects without any reference.
Be careful: Garbage collection reclaims the memory space occupied by objects without any reference, not the objects themselves,2,GC Two algorithms of recovery mechanism,a, Reference counting b, Reachability analysis algorithm(
Accessibility here, You can see the basics2 Java What period of an object), As for the more detailedGC Algorithm Introduction, You can refer to:Java GC Mechanism algorithm

2,Java Object lifecycle

answer: Creation phase , Application stage , Invisible phase , Unreachable stage , Collection phase , End stage, Object space reallocation phase and so on, Specific reference:Java Object lifecycle

3,Map perhapsHashMap Storage principle of

answer:HashMap Is an array+ A structure of linked list, Specific reference:HashMap Implementation principle of

4, When data tableA,B Combined index of fields, Then use it aloneA Or use aloneB Will it be indexed?( Uselike How does query have index effect)


answer: seeA,B When two fields are combined for index, Who is in front? Who is behind? IfA Before, Then use it aloneA There will be an indexing effect, Use aloneB No, Vice versa. Empathy, Uselike Fuzzy query, If you just use the front%, So it has index effect, If double% Number matching, Then there is no index effect

5, When database stores date format, How to consider time zone conversion?

answer: UseTimeStamp , Cause reference:Java Time zone conversion problems encountered in programming

6,JavaObject What are the methods in the class?

answer:Object What are the methods

7,HTTP Agreement,GET andPOST Difference

answer: Talking aboutHTTP inGET andPOST Difference

Four, thread, Design pattern, Cache aspect

1,SimpleDataFormat Non thread safe, How to use it better and avoid risks

answer: aboutSimpleDateFormat Safe time format thread safety

2, How to treat design pattern, And briefly talk about your understanding of the observer model

answer:1, The design mode is used by Magic Horse2, Observer pattern class diagram and its implementation

3, In cluster environment,session How to share

answer:1,Java Clustersession Share2,session Multi server sharing scheme, Another solution is to use a fixed server to maintainsession, Shared by other servers

4, Distributed, In cluster environment, How to refresh the cache, How to keep in sync?

answer:A, How to refresh the cache?1, Timed refresh 2, Active refresh override, Each caching framework has its own refresh mechanism, Or cache invalidation mechanism, TakeRedis and Ehcache Give an example,
They all have their own expiration mechanisms, In addition, when actively refreshing the overlay, Just get the correspondingkey Just overwrite the data

B, How to keep cache synchronized?
thisredis Cluster synchronization mechanism with its own, Copy function, Specific reference: Be based onRedis Distributed cache implementation,Ehcache There are also distributed cache synchronization configurations, Just configure different server addresses, Reference:Ehcache Distributed cache synchronization

5, One articlesql Long execution time, How do you optimize, From what aspects?

answer:1, Seesql Whether to involve multi table joint table or sub query, If there is, See if business splitting can be performed, Relevant fields are redundant or merged into temporary tables( Business and algorithm optimization)

2, Queries involving linked lists, Whether to query by table, Field integration of results after single table query

3, If neither of the above can be operated, Non linked list query, Consider indexing the corresponding query conditions. Speed up query

4, History table separation for large number of tables( Such as transaction flow sheet)

5, Database master-slave separation, Read / write separation, Reduce the pressure of reading and writing to the same table at the same time, As for master-slave synchronization,MySQL Self possessedbinlog Realization Master slave synchronization

6,explain Analysissql Sentence, View execution plan, Whether the analysis index is used, Analyze scan lines, etc

7, Seemysql Execution log, See if there are other problems

Personal understanding: Basically, Query slow is occupiedmysql More memory, Then we can consider it from this aspect

Five, Design related

The interview will also ask some questions about the design, such as

1, Your interface service data has been intercepted, How do you prevent data from being submitted maliciously?


answer: We can set a service number in the interface transmission parameters, This number is used to distinguish whether to submit repeatedly. So even if the data gets caught, The other side can't distinguish what you mean by each field, Then, The function of this business number is coming

2, Suppose the server often goes down, How do you check the problem?

answer: I'll leave this for you to add, Reply with comments

All in all, we have to see, Still have to learn学.再次强调,基础很重要!面试技巧同样很重要,还是那句话:祝愿各位看官都能找到心仪的工作吧~~

另外,奉劝大家不要频繁跳槽,这些知识点能提升固然好,不要盲目跳槽,找工作很累的,而且没有哪家公司喜欢频繁跳槽的员工

Java程序猿跳槽应该学哪些方面的技术

互联网产品,大型企业级项目常会用到的:

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并发处理技术.具体到Java上通常是涉及java.util.concurrent,并发锁机制,NIO等方面,当然最近比较火爆的Netty框架也可以作为高并发处理的备选方案之一,这需要对Java的线程调度机制有着比较深的理解.不过这些可能会涉及并发控制的对象(比如reentrantlock等)只能存在于一个JVM里的问题,一旦系统规模大到需要部署多个JVM来处理并发的情况,则需要采用共享session的技术(比如spring-session),或者尽可能将系统后台设计为无状态的服务,这需要对RESTful有着较深的理解.

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高可用,负载均衡技术.互联网产品,企业级应用通常要求一年里的Downtime控制在很小的范围内,这需要足够的高可用和负载均衡架构来支撑,这个一般和Java技术本身没太大关系,但却是一名初级程序员向高级程序员甚至是架构师CIO进阶的必备技术,因此可以适当了解一下Nginx,HAProxy等对这方面的支持.另外现在最“时髦”的做法是将应用docker化,配合ETCD,kubernetes等工具在容器的层面上实现高可用和负载均衡,当然这需要看实际的需求,最时髦的不见得是最适用的,要考虑构建成本.

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缓存技术.缓存应该是大型系统中或高并发条件下提高响应速度的亘古不变的真理(虽然也看到过淘宝搜索商品功能采用的大数据处理技术实现的零缓存的文章,但能达到淘宝的体量和技术水平一般不太可能),这方面的工具太多了,ehcache,memcached,redis……从Java的角度来讲,需要了解的一是Java对这些工具的连接器,二是缓存技术背后的JSR-107标准,可以参考spring-cache的实现,阅读一下源码加深理解.

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异步处理技术.这通常也是抵消高并发的处理手段之一,从Java的角度看最简单的异步处理就是新启动一个异步线程,这同样也需要对Java的线程调度有所了解,当然也可使用Spring中的@Async之类的也可以简单实现异步线程的处理.如果是非常消耗资源的业务处理,简单的异步线程是满足不了需求的,这就需要一些消息中间件来做这些异步处理了,消息中间件有很多,activemq,rabbitmq,kafka……需要了解的是Java对这些中间件的连接器.不过异步处理中最关键的是事务保证的问题,这可能需要对事务的两步提交有所了解.

在这里我有一个专门为跳槽JAVA开发人员想要跳槽准备的一个线路图:

一共分为5大专题:


高并发专题:



应用框架专题:



工程化管理专题:



双十一架构:



性能优化: