2019 autumn recruit Ali Java interview questions (with answers), Ali is waiting for you
Preface:
Preparing for September and October can not escape the tortured soul of the interviewer, I compiled some Java interview questions for everyone to share, because of space limitations, only a portion with the answer, you need to face these questions receive answers add my qq group 778 477 315 to receive a free
1. How to achieve an efficient way linked list in reverse order output?
The answer: a small list head recursive output interpolation
2. Known sqrt (2) is approximately equal to 1.414, requires no math library, seeking sqrt (2) after 10 decimal places; Note: sqrt is the square root of the mean!
Answer: binary search
3 Given a binary search tree (BST), find a small tree in the K-node
Answer: recursive query method
4.LRU caching mechanism
The answer: map stored value
5. With regard to epoll and select the distinction, which of the following statements are true
Answer: About epoll and select the difference between what is right?
6. From the index structure innodb analysis of why the index key length is not too long
Answer: Analysis and innodb myisam
How 7.MySQL data recovery to any point in time?
The answer: to restore to any point in time to do regular full backup, incremental backup and binlog log as a precondition. After the recovery to any point in time the first full backup to restore, and then played back on the basis of increased binlog until a specified point in time.
mysqlbinlog - stop-datetime = "2018-02-19 23:57:02" mysql-bin.000088; Alternatively, you can select their own starting point recovery --start-datetime = "2005-04-2010: 01: 00"
8.NFS and SMB are the two most common NAS (Network Attached Storage) protocol, when a file system to be shared with multiple hosts simultaneously via NFS and SMB protocol access, which of the following statements is wrong
The answer: the difference between NFS and SMB
9. Enter the ping IP hit enter, what will happen before the contract?
Answer: Path request
When under 10. Please explain why Luhan published romance, microblogging system will collapse, how to solve?
答案：从三个角度分析
11.现有一批邮件需要发送给订阅顾客，且有一个集群（集群的节点数不定，会动态扩容缩容）来负责具体的邮件发送任务，如何让系统尽快地完成发送？
答案：
A. 借助消息中间件，通过发布者订阅者模式来进行任务分配
B. master-slave 部署，由 master 来分配任务
C. 不借助任何中间件，且所有节点均等。通过数据库的 update-returning，从而实现节点之间任务的互斥
12.有一批气象观测站，现需要获取这些站点的观测数据，并存储到 Hive 中。但是气象局只提供了 api 查询，每次只能查询单个观测点。那么如果能够方便快速地获取到所有的观测点的数据？
答案：
A. 通过 shell 或 python 等调用 api，结果先暂存本地，最后将本地文件上传到 Hive 中。
B. 通过 datax 的 httpReader 和 hdfsWriter 插件，从而获取所需的数据。
C. 比较理想的回答，是在计算引擎的 UDF 中调用查询 api，执行UDF 的查询结果存储到对应的表中。一方面，不需要同步任务的导出导入；另一方面，计算引擎的分布式框架天生提供了分布式、容错、并发等特性。
13.如何实现两金额数据相加（最多小数点两位）
答案：
其实问题并不难，就是考察候选人对 JavaScript 数据运算上的认知以及考虑问题的缜密程度，有很多坑，可以用在笔试题，如果用在面试，回答过程中还可以随机加入有很多计算机基础的延伸。
回到这个问题，由于直接浮点相与加会失精，所以要转整数；（可以插入问遇到过吗？是否可以举个例子？）。
转整数是第一个坑，虽然只有两位可以通过乘以100转整数，但由于乘以一百和除以一百都会出现浮点数的运算，所以也会失精，还是要通过字符串来转；（可以插入问字符串转整数有几种方式？）字符串转整是第二个坑，因为最后要对齐计算，如果没考虑周全先toFixed(2)，对于只有一位小数点数据进入计算就会错误；转整数后的计算是个加分点，很多同学往往就是直接算了，如果可以考虑大数计算的场景，恭喜同学进入隐藏关卡，这就会涉及如何有效循环、遍历、算法复杂度的问题。
14.关于并行计算的一些基础开放问题
答案：各种指令
15.请计算XILINX公司VU9P芯片的算力相当于多少TOPS，给出计算过程与公式
答案：基于不同的算法，这个值在十几到几百之间。但是，如果只是单纯比算力，FPGA和ASIC、GPU相比并无太大优势，甚至大多时候有较大劣势。FPGA的优势在于高度的灵活性和算法的针对性。
16.一颗现代处理器，每秒大概可以执行多少条简单的MOV指令，有哪些主要的影响因素
答案： 及格： 每执行一条mov指令需要消耗1个时钟周期，所以每秒执行的mov指令和CPU主频相关。
加分： 在CPU微架构上，要考虑数据预取，乱序执行，多发射，内存stall(前端stall和后端stall)等诸多因素，因此除了cpu主频外，还和流水线上的效率(IPC)强相关，比较复杂的一个问题。
17.请分析 MaxCompute 产品与分布式技术的关系、当前大数据计算平台类产品的市场现状和发展趋势
答案：开放性问题，无标准答案。
18.对大数据平台中的元数据管理是怎么理解的，元数据收集管理体系是怎么样的，会对大数据应用有什么样的影响
答案：开放性问题，无标准答案。
19.你理解常见如阿里，和友商大数据平台的技术体系差异以及发展趋势和技术瓶颈，在存储和计算两个方面进行概述
答案：开放性问题，无标准答案。
20.在云计算大数据处理场景中，每天运行着成千上万的任务，每个任务都要进行 IO 读写。存储系统为了更好的服务，经常会保证高优先级的任务优先执行。当多个作业或用户访问存储系统时,如何保证优先级和公平性
答案：开放性问题，无标准答案。
21.最大频率栈
22. Given a list, delete list penultimate N nodes, and returns the list of the first node
23. If you could design a universal, support a variety of database-level backup and restore of the second system, how would you design
24. If you were to design a database support, data flow and processing of real-time flow of data between NOSQL and big data, what issues would you consider? How to design?
25. Given an integer a and an integer array, returns the index of the two arrays, two index points and plus numbers equal to a specified integer. Require optimal algorithm, space and time complexity analysis of algorithms
26. If you give a new product, you will what to protect its quality?
27. Please evaluate the results of the program?
28. How can I test a bike?
29. How to determine whether the two lists intersect?
to sum up:
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