Interview Summary--java senior Engineer (III)

First, Monologue

Before interviewing others, now it's your turn to find a job, how to say, each interviewer's views are different, interview the way is not the same, for example, I interview others I like to ask the project he used those, and then to use the technology to ask some questions, or some of the scenarios of some technical implementation of the program is my special like to ask,    For example , when your interface service data is intercepted by someone, how do you prevent the data from being maliciously submitted? Relatively speaking, the bottom of Java and the Foundation will ask less, of course, ask less than the representative does not ask, but the focus is on the project you have done and how you design ideas. Of course, understanding the basic and the bottom is better, so that you know it, better know why, the code and program written out more robust and maintainable. So, the foundation is still very important.

Now it's my turn to go out for an interview, how to say, in fact, still quite nervous, thought that he would not be nervous or anxious, in fact, or some, in not finding the right job, or even a little sleep at night, always feel that there is something pressing in my heart, sleep is not at ease. Since can't sleep, that still look at the data bar, I have a habit, sleep before the problem, the next morning can think of the answer, before bedtime to remember the information, the next morning can remember particularly deep, do not say nonsense, directly into the topic bar.

second, interview skills

1, memorize your CV

Why: The first question of the interview is generally to let you introduce yourself briefly, or introduce your recent project, and an interviewer, if not even their own resume is not familiar with the project, the technology can not be described clearly, I think no company will accept this, even if you are super talent, You are not self-expression, estimates will also be a headache, so, remember: be sure to recite your resume, do not require you to write down all, at least to memorize the two companies you have been recently, the two companies within the project you have done, you are responsible for the module, The technology used in the project and the relative technical implementation of the scheme (this is particularly important).

2. In-depth knowledge and memorize some Java basics

Reason: Most companies, regardless of the initial interview or high-level, whether it is a written test or interview, will ask a series of basic questions, these basic questions about the JVM, strings, collections, threads, and so on, if each let you memorize you must not remember, then is the understanding of memory, with the JVM, If you want to talk about your understanding of the JVM, you first need to know what structure the JVM is made of, what each structure is used for, and then consider how a Java object is built from creation to recycling, and how the JVM is structured in such a way. If you synthesize memory from these aspects, believe in less, and you understand more thoroughly. As for if you want to talk about collections, such as the difference between a set of Arrylist, LinkedList, vectors, and so on, the same way, you need to understand what the structure of each one is, and you will know what it does, so you'll be more refined in your usual usage. And in the interview process, also not speechless.

3, maintain self-confidence and a heavy calm mentality

Reason: During the interview process, self-confidence is indispensable, I believe you can, interview on the way you can say to yourself: I belive I can! Anyway, I do so, the heart of the ego implies that, in fact, in the face of the interviewer, your confident state will let the interviewer feel that you are a very strong person, at least from the feeling will give you a high score.   There is also to maintain a heavy calm, if it is to provide you with technical solutions or a technical principle, there is no need for a nervous grunt of anything said, you can say to the interviewer: I think first, and then assemble their own memory knowledge, assemble the language, organized to say, so that can better performance of your talent, is not it? Interview who will be nervous, I will be nervous, sometimes clearly remember the knowledge points forget, it's OK, Bold said forget, or directly say do not know. Keep in mind that some parts don't know it's okay, if you know it all, then you should be the CTO level (joking).

4, try to remember the interview process you do not answer or answer the question of improper

Reason: The interview failed, after all, each company's requirements are not the same, ask questions and you are good at the aspects may be different, but please remember that you can not answer questions in the interview, or you feel that the answer is not very accurate questions, you write down, if not, You can ask the interviewer on the spot whether there is a good answer, if the interviewer is not willing to tell you (generally the basic aspects of the interviewer will not bother to answer you), then you go home slowly check the information, if it is some specific technology, you can write your own case or something, after all, the knowledge point is so much, the problem is unchanged Interviewing is also a learning process that allows you to understand the technologies that most companies currently need or require. I don't know this time, I'll know next time.

5, before you go to the interview, it is best to understand the situation you want to interview the company (including products, project situation)

Reason: As the saying goes, the Baizhanbudai, the interview is a battle, you need to understand your interview company Basic situation, including the job requirements, so you can probably know that you need to interview the company's technical requirements. Why do you know the company's main products and projects, is to give you a general understanding of the company's technical structure of the situation, including you may be to their implementation of a way to challenge and doubt, I believe the interviewer is willing to help you answer these questions. So you have both the performance, but also learned the knowledge, why not.

6, reasonable arrangements for your interview time (if there are many companies interview opportunities, try to put the company you want to go to the end of the interview)

Reason: It is estimated that many people do not understand this, probably most people are confused about how to arrange interview time, randomly arranged.  But here's a trick, if you have multiple interview opportunities at the same time, you put the company you most want to go to the end of the interview, so you go through the front of these company screening, if successful is a chance, if not successful, but also for the final cushion. But here you need to consider two points: 1, you need to remember the company and the basic situation of your resume (this means you are not a sea-casting) 2, if not remember, then you can answer a time, follow-up understanding of company information, by mail or other means with their agreement, adjust the interview time. and it is recommended to arrange a day of interview companies not more than two, the best is the morning one, the afternoon, so you can have sufficient time to adjust the state.

Basic Summary of interview questions

1, the JVM structure principle, the GC working mechanism detailed

A: Specific reference: JVM structure, GC working mechanism in detail, when it comes to GC, remember two points:1, GC is responsible for reclaiming all the memory space without any reference object. Note: Garbage collection is collected without any reference to the object occupied by the memory space instead of the object itself,2, GC recycling mechanism of two algorithms, a, reference counting method B, the Accessibility analysis algorithm (here, you can see the basic 2 Java object of what period), as for more detailed GC algorithm introduction, You can refer to: Java GC mechanism algorithm

2. The life cycle of Java objects

A: Create phase, application phase, invisible stage, unreachable stage, collection stage, end stage, object space redistribution phase, and more, refer to: Java object life cycle

3, map or HashMap storage principle

A: HashMap is a structure of the array + linked list, the specific reference: HASHMAP implementation principle

4. When a and B fields in a data table are indexed together, will there be an index effect by using a alone or using B alone? (How to use a like query for indexed effects)

A: Look at a, B two fields do the combination index, who in front, who in the back, if a in front, then use a alone will have an index effect, using B alone is not, and vice versa. Similarly, when using a like fuzzy query, if you use only the previous%, then there is an index effect, if you use a double% number match, then no index effect

5, how to consider the time zone conversion problem when the database stores the date format?

A: Using timestamp, reason reference: time zone conversion problems encountered in Java programming

6. What are the methods in the Java object class?

Answer: What are the methods of object

7. HTTP protocol, the difference between get and post

A: Talking about the difference between get and post in HTTP

iv. threading, design patterns, caching aspects

1, Simpledataformat is non-thread-safe, how to better use and avoid the risk?

Answer: About SimpleDateFormat security time-formatted thread safety issues

2, how to look at the design pattern, and simply say your understanding of the observer pattern

A: 1, the design mode of God Horse 2, the observer pattern and the implementation of the class diagram

3, in the cluster environment, the session how to realize sharing

A: 1, the Java cluster session sharing 2, session multi-server sharing scheme, there is a solution is to use a fixed server dedicated to maintain session, other servers share

4, distributed, cluster environment, how to refresh the cache, how to keep in sync?

A: How does the cache refresh? 1, timed refresh 2, active refresh coverage, each cache frame has its own refresh mechanism, or cache invalidation mechanism, take redis and Ehcache for example, they have their own expiration mechanism, in addition to actively refresh the overlay, just get the corresponding key to cover the data can be

B. How does the cache stay in sync? This redis has its own cluster synchronization mechanism, that is, the replication function, specific reference: based on the Redis distributed cache implementation, Ehcache also has distributed cache synchronization configuration, only need to configure a different server address, reference: Ehcache Distributed Cache synchronization

5, a SQL execution too long time, how do you optimize, from what?

A: 1, to see whether SQL involves multiple tables or subqueries, if any, to see if the business can be split, related fields redundant or merged into a temporary table (Business and algorithm optimization)
2, related to the list of queries, whether it can be divided into table query, the results of a single table query after the field integration
3, if the above two can not operate, not to list query, then consider the corresponding query conditions to do the index. Speed up queries
4, for a large number of tables for the separation of historical tables (such as the trade table)
5, the database master-slave separation, read and write separation, reduce reading and writing for the same table pressure, as for master-slave synchronization, MySQL has its own binlog to achieve master-slave synchronization

6, explain analysis SQL statement, view execution plan, analyze index is used, analyze scan line number, etc.

7. Check the MySQL execution log to see if there are any other issues

Personal understanding: Fundamentally, the query is slow to occupy more than MySQL memory, then you can consider this aspect of the hand

v. Design program related

The interview will also ask questions about design options, such as

1, your interface service data is truncated, how do you prevent malicious data submission?

A: We can set a business number in the interface transfer parameter, which is used to distinguish whether or not to commit repeatedly. So even if the data is captured, the other party can not distinguish the meaning of each field, then the role of this business number is coming

2, if the server is often down, where do you troubleshoot the problem?

A: This will be left for you crossing added, can comment reply

Interview Skills to supplement these, if you remember anything in addition, if there are other small partners have other suggestions can also be in the comments reply, other interview questions include algorithms, data structure, HTTP protocol and so on, these waiting for everyone to supplement their study, Spring principle, Spring MVC principle asked a lot of, you have time to see the previous interview summary-Advanced Java Engineering (a) and interview summary-Senior Java Engineer (ii).

In a word, the view is still to be seen, but also to learn. again, the basics are important! Interview skills are also important, or that sentence: I wish you all crossing can find the right job ~ ~

In addition, we advise you not to frequent job-hopping, these knowledge points can be improved is good, do not blindly job-hopping, looking for work is very tired, and no company likes frequent job-hopping staff

Interview Summary--java senior Engineer (III)