North of Guangzhou-Shenzhen, 2020, the number K of Java programmers should understand multi-threaded and highly concurrent JVM optimization

Primary - elementary
grasp java-based, familiar with common libraries. Javaweb understanding of the servlet, JSP, and understand the principles common framework java web package, it is possible to complete the frame by means of CRUD function. Understanding of the status of the database in web development.

Primary - in order
appreciated java the more advanced features, such as reflection, dynamic proxies, the JVM, memory model, multi-threading and the like. Skilled use of the framework, the framework of bug encountered, able to analyze the cause of the problem by means of the log and search engines. In the team, able to finish the development of the general background of business functions. Learn advanced database features such as indexing, storage, engine and so on.

Primary - High
understood java distributed architecture, micro-services architecture (e.g., rpc frame dubbo, motan, or a Class springcloud) to understand the difference with centralized architecture, and to ensure the quality of distributed codes. Familiar with various middleware such as redis, mq, zookeeper and so on, and see how it works and usage scenarios. Under the able leadership of intermediate or advanced programmer to complete the research and development of non-core functions. To focus on open source, and has the ability to read source code.

Intermediate
primary high-order has been very powerful, but often lack the experience of some projects, so I'm here or junior. From junior programmer only needs the support of the technical aspects, but also need to have some experience in the development project (over 3 years of front-line Internet product development experience), with a line of bug processing power, JVM has the ability to adjust and complete the core business functions development. And led the team of newcomers, you can assign tasks according to ability. (Wanted to make junior high order is divided into intermediate elementary, but I still feel necessary intermediate level is the ability to solve the bug online)

Senior
team core characters, control the quality of the entire project, including code loopholes and regulatory issues. It has more than 5 years project development experience, 2 years experience in architecture built, can be selected according to service different types of architecture; according to the composition of the team, assign different tasks. It has the ability to share their knowledge out to lead the junior programmers to intermediate, intermediate to advanced programmers the ability.

 

Multi-threaded and highly concurrent

 

 

JVM tuning of case-combat guidance

 

First, why is there a multi-threaded concurrency issues

Why multiple threads simultaneously access (read and write) with variables, there will be complicated by the problem?

1. Java memory model specifies all the variables are stored in main memory, each thread has its own working memory.
2. Working memory thread stored in the main memory copy of a copy of the variables used in the thread, the thread all operations on the variables must be in working memory, but can not read and write directly to main memory.
3. Threads access a variable, the first variable from main memory into the working memory copy, write to the variable, not immediately synchronized to the main memory.
4. Between different threads can not directly access the working memory of the other variables, the variables are passed between threads require data between their working memory and main memory simultaneously.

Two, Java Memory Model (JMM)

Java Memory Model (JMM) acting on the data synchronization process between working memory (local memory) and the main memory, which specifies what to do and when to do data synchronization data synchronization, as shown below.

 

Third, complicated by three factors

Atomicity : In one operation, the CPU can not then be suspended in the middle of scheduling, i.e. the operation is not interrupted, or executed, or not executed.

Visibility : When multiple threads access the same variable, a thread changes the value of this variable, other threads can immediately see the modified values.

Ordering : the program execution sequence performed in the order code.

recommend:

Hardcore sweeping God had "Mashi Bing" published in the "multi-threaded and highly concurrent," you deserve 2020

Fans made a year ago to participate in a list of interview questions NB Enterprises:

1. Talk synchronized CPU primitive level of realization
2. Ten million number, write a program for efficient summing
3. Known 2 1.414 square root, how to do math library, find the square root of value, accurate to 10 decimal point behind children
4. 编码实现两个线程，线程A不断打印1-10的数字，要求在打印到第五个数字的时候通知线程B
5. 自定义线程池需要指定哪7个参数，为什么不建议使用JUC内置线程池？
6. 高并发、任务执行时间短的业务怎样使用线程池？
7. 并发不高、任务执行时间长的业务怎样使用线程池？
8. 并发高、业务执行时间长的业务怎样使用线程池？
9. 设计一个12306网站，能够撑住最高百万级别TPS（淘宝最高54万TPS），你该如何实现？

如果你平时只有CRUD的经验，从来不会了解多线程与高并发，相信你一定一头雾水。

如果是这样，建议各位读者朋友接着往下看。

今天小编分享一位骨灰级扫地神僧“马士兵”出版的《多线程与高并发》，这两大块儿是现在面试问的越来越多，也是相对一个初级的程序员向中高级迈进的必须要踏过的一个坎儿。本书籍带你将多线程的知识系统化，帮助你理解多线程在CPU层级的实现，以及这些实现如何一层一层的映射到那些上亿用户，千万QPS，百万TPS的系统。

横扫一切关于多线程的问题，吊打所有敢于提问并发问题的面试官。（面试官大佬别放心上哈）

本书籍是使用比较口语化的文字形成一本书，通俗易懂，让各位读者朋友们可以花费更少时间做最有效的学习。

《多线程与高并发》共由九节组成

第一节：线程的基本概念

 

 

第二节：volatile与CAS

 

 

第三节：Atomic类和线程同步新机制

 

 

第四节：LockSupport、淘宝面试题与源码阅读方法论

 

 

第五节：AQS源码阅读与强软弱虚4种引用以及ThreadLocal原理与源码

 

 

第六节：并发容器

 

 

第七节：线程池

 

 

第八节：线程池与源码阅读

 

 

第九节：JMH与Disrupor

 

 

由于篇幅限制这里只能给大家把内容部分截取出来，因为此书籍资料是为内部资料，需要获取完整电子版/实体书籍以及实体书籍的读者朋友们转发分享此文，私信本人：【马士兵】获取！

实体书籍

 

 

《多线程与高并发》电子版

 

 

Due to space limitations here can only give you part of the contents of interception, because this information is for internal information books, you need to get the full electronic version / physical books as well as physical book readers and friends to share this article forwarding, private letters I: [ Mashi Bing ] Obtain! (Thank you readers!)