A company Java development face test

First side
Project:
1, find a project, introduction of the situation. What problems are encountered and how each problem is solved.
Algorithm title:
2, a sorted array, find out the sum of two of all the combination of M
3, natural number sequence, to find any contiguous and equal to N of all the subsequence
Data:
4, from the database to find a data result set, which has a time field, please use a data structure storage so that you can quickly detect a period of time records.
5. I mentioned the B + tree in the previous question, and he went on to ask why we used the B + tree to index without the binary tree.
Database:
6, talk about the Oracle database transaction isolation level, and the related problems encountered
I said this. Standard four levels, three levels of Oracle implementation, and overview of the next multiple version read consistency
Project related technology:
7, see the resume wrote an RPC, speaking, I said with RMI more like, said the similarities and differences, and then expand to the memory allocation problem, but did not understand what he was going to say. Also problem Java client and C program server communication, such as C over there directly a structure to come over, how to deal with the answer Yue never met.
8, on the resume of the JVM performance tuning, say what has been done
9. When it comes to the JVM, when it comes to our use of Windows development, ask the Linux script, you know, awk used it?
10, resume writing web framework development maintenance, ask the browser end and server-side how to communicate, but finally only fell to the Java object How to pass to the client, the client data how to pass to the service side.
Java Basics:
11, the problem of concurrent synchronization, synchorized is how to use, the object of wait, notify method what role
Framework:
12. Understand the implementation of SPRING,IOC, the implementation of AOP, what are the limitations of various schemes

Second side
Project:
1, introduce you to do the project, a little high-level introduction, meaning is not endless introduction
It mentions how the singleton state of the primary instance cluster node and the primary instance standby node remains synchronized
2, RPC communication and RMI differences
3, concurrent access to the same data, how to ensure data synchronization.
4, the website performance optimization has done what, concrete. ETag, Last-modified, Expires, Cache-control
5. What is the most impressive book that you have seen recently?
Algorithm:
6, Binary tree, find two nodes at the lowest level of the public parent node, to give ideas
7, one-way linked list inversion, write code

On the third side (remember so much)
Self Introduction:
1, the personal basic situation, by the way mentioned project, began to pull a few
Database:
2, database performance optimization have to do. Do something about it.
Design:
3, design a small store invoicing system of the table structure design, the boss every day to know the goods sold, to regularly check the cost of goods, sales and profits.
Here to note that one of the key points is how to carry out cost calculation, to know the cost calculation of several methods, choose one of the implementation, this will affect the design of the table structure
Algorithm:
4, 1 to 100 million of the natural number, the sum of the numbers after the split of all numbers, such as 286 split into 2, 8, 6, such as 1 to 11 after the split number and => 1 + ... + 9 + 1 + 0 + 1 + 1.

Before going to Baidu interview, sorting out the interview question. No written test, talk directly with the interviewer. I feel the interview is very good, very patient, every interview back regardless of company size, whether or not to get an offer, but the basic can have some valuable input, and quite happy. Although I have 4 years of work experience, but is not the department of Pure Technology, development, maintenance, see customers, project management, what have been done, recently want to change jobs, feces hair map strong evil complement algorithm, data structure of a large company special love Test basic knowledge.
This is a bad answer to the latter few questions. In particular, there is a server session optimization and database table horizontal split strategy, did not mention a bit, back on the road with a little thought, back to Baidu, found sorta. The previous several algorithms are also bumps, at least, said up, is not the best is not easy to say.
Before doing information systems, pay more attention to the business and the realization of the function, although everyone shouted performance, architecture, what, but in fact no one cares. It's just a bit of a person to hang out with anyway. Internet companies are really different, and the focus on concurrency and large amounts of data is deep in the marrow. Feel really ashamed. Although these few years running customers talk about the needs of the PPT is also a mixed scene, but from the heart hope that they can be a further step in the technology.


According to the memory collation as follows:

1. There is a set a, which has n a positive integer, in a disorderly order. Given a positive integer n, the sum of any two numbers in a is equal to n, and what kinds of combinations are in common. For example, if the collection is {1,3,44,2,4,5,54,222,368} n=6, the result set is {1,5},{2,4}
This problem is similar on the internet

2. The realization of TreeMap.
The structure and advantages and disadvantages of various collection classes, we all love to test. Used to do industry information, there is no feeling, but if you care about performance, it is very useful to find out.

3. There are two very large files, each of which has 100 million rows, one integer per line. Ask what the intersection of these two sets is. Given the premise that the machine does not have enough memory to fully load any one file.
This is almost the original question on the Internet.

4. Heap and stack definition, heap and stack inside the object, which runs faster.
Also asked a number of derivative questions, not clear, as long as the Java textbook on this aspect of the introduction enough

5. In order to implement a line chart, the data needs to be deposited into a structure, the line chart is the time, the ordinate is the value, the regular query is to query by time, such as select value from T where begin> ' 20110101 ' and end< ' 20111212 ', it's better to use that kind of data structure in Java.
Or test Java in a variety of collection classes, essentially ask the various data structures in the sequential/random read/Insert efficiency

6. The index of the database is usually implemented with what data structure. Why use this data structure.
Know is btree, but Btree is the story, why not with other tree or other structure, this read a post before understand. is a study.

7. If there are 2 tables in the database, the table A field is the name, the age, and the table B field is the name, the unit. Now use the last Name field to make a left join query, assuming that the last Name field is indexed. Ask how the database is implemented. If you look at the two tables as an array in memory, you can implement the LEFT join yourself.
Interviewer see I really do not know how the database leftjoin how to achieve, let me implement an in-memory, reluctantly answered it, but may not be very good.

8. Database various transaction isolation levels
This is pure do not remember, before the work never used, really ashamed.

9. Wait () method and Notify () method of what to use, wait () method has any use restrictions, where can be used.
For a person who has never used multiple threads, such a simple question becomes a bit difficult. Only know what to do with, do not know what is the limit.

10. The database has a table with hundreds of billions of data, how to optimize. (mainly split, apart from the business, what else from the technical point of view, scalability, good horizontal split way)
The idea is to dismantle the right, but the interviewer is not asking the business split strategy, but the technical considerations. Also have to consider extensibility, such as after the demolition, the volume of data growth quickly, but also demolished, how to do. This horizontal split strategy has a lot of, online can search. But I said is not very systematic, has not been done before, are the scene to think.

PS: At the time of the new Oriental, the teacher said, sometimes although your English is not good, but there are a few words as long as you remember, said when stuffed into the sentence, people will feel that you specially way,
Like Absolutely. I think the interview also has this key words, such as a bit sort of stream, said when still have to special juchongruoqing. Suitable for all kinds of novice and at ordinary times in the work of the people do not use a variety of sorting algorithms,

Theme: Taobao Beijing special Java Face test questions (2011-12-31)

First side
1, talk about the project
Because I have been a product for several years, from the backstage to do the foreground, from the business development to achieve technology platform, so the entire product deployment map, b/S & C/S, and then a layer of explanation.
b/S existing Web framework transformation, browser caching, c/s patch download various ways, CDN, C/S communication protocol, RPC cluster, HTTP cluster, load balancing, cluster front machine scheduling, back-end server master-slave instance, back-end server various optimization (asynchronous, performance isolation), Database server Optimization (index, materialized view, read-write separation, account set carry-over, database horizontal segmentation, vertical segmentation), inter-layer call performance monitoring, control the various parts of the product map down.
2, HTTP cluster scheme, we are the reverse proxy server, their own write proxy server, can also use the mainstream of the Web server, and then the interviewer asked Ngnix, LIGHTTPD, Apache three major web server differences ... It's embarrassing.
3. What would you do if you had the opportunity to redesign your product?
This answer is not good, mainly from the communication protocol and data storage two to say, this is a bit one-sided. Because of our product itself and a lot of problems, only through the deployment of frame composition is not reflected, such as two development issues, patch download problems, different modules of the Java Package Interdependence, technical framework is more closed, the construction system scheme behind, the lack of documentation, etc., we have experienced a lot of pain inside, But at the time the mind was confined to the deployment framework, so it did not say these questions.
Second side
4, how to optimize the performance of the website.
A little bit of your website performance optimization experience, combined with the "Build high-performance Web Site", pull a pass, with a bit similar to one side.
5, originally want to spend the product structure diagram, I turned over the resume, there is a time behind the painting, there is no painting. Then I'm going to draw the JVM architecture on the blackboard (called the blackboard).
Draw the JVM architecture, explain the JVM components and components of the interaction, GC algorithm, a variety of garbage collectors, run-time optimization, products encountered in the JVM-related issues such as oom, classloader issues, and the implementation of the Hotspot VM to explain the heap, not heap memory partition
Third side (HR side)
6, look at my face of business-to-business and Alipay, asked the next situation
The business-to-business is over, but it's not over; Alipay has passed 2 sides.
7, personal advantages and disadvantages
8. Would you like to come to Hangzhou
The four side (video phone face, a Daniel in Hangzhou)
9, the introduction of the project. On the transformation of web framework, the similarities and differences with the original frame
10, after work time has the study technology?
11, whether to participate in the Open source project

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Sorry, is 2011-12-31, the harm of everyone thread through ...
I work time is not short, 4.5 of small Ben. This face, over the P6, Taobao Mall business Development department.
The previous three years is to do ERP business development, technology has nothing to upgrade. The last two years in the platform department, half a year ago feel mixed up quickly hung up the company's documents, read the source code, reading. The specific interview is prepared for a few days to write another article. Recently, only a few interview questions, in the blog, just to send out to share, but also because some colleagues want to know the interview content of these companies. In addition, in order to eliminate the fear before the interview of some companies like me---I have not had the confidence before the face of Baidu, do not know what they meet, the internet did not find the complete topic of the Java interview .... Je jar of cattle, and please feel free.