Preface
Multithreading and high concurrency are already the must-question points for interviews of major companies, and they are also the hurdles that junior programmers must step through to advance to the middle and advanced levels. In this article, let’s talk about multi-threading and high concurrency. At the beginning of the article, let’s take a look at some real interview questions about multi-threading and high concurrency from big companies such as Baidu, Meituan, Ali, SF, and Jingdong. See how many answers you can answer.
- Please describe the underlying implementation of synchronized and reentrantlock and the underlying principle of reentrance-Baidu Ali
- Please describe the four lock states and the upgrade process-Baidu Ali
- How to solve CAS's ABA problem-Baidu
- Please talk—under AQs, why the bottom layer of AQS is CAS + volatile-Baidu
- Please talk about your understanding of volatile-Meituan Ali
- How the visibility of volatile and the prohibition of instruction reordering are achieved-Meituan
- What is CAS-Meituan
- Please describe the process of object creation-Meituan SF
- Memory layout of objects in memory-Meituan SF
- Why add volatile to DCL singleton-美团
- Explain the four states of locks-SF Express
- How many bytes does Object o = new Object() occupy in memory?--SF
- Please describe the similarities and differences between synchronized and ReentrantLock-SF
- Talk about your understanding of as-if-serial and happens-before semantics-Jingdong
- Do you know ThreadLocal? Do you know how to solve the memory leak problem in ThreadLocal?-Jingdong Ali
- Please describe the classification of locks and the application in DK-Ali
- Is the white spin lock necessarily more efficient than the heavyweight lock?-Ali
- Will the efficiency of opening the bias lock be improved? Why?
Why is it so important to master multithreading technology now
how about it? Does it feel a little awkward to look at. When I first saw it, the editor was also confused. It can be said that multithreading technology is now the basic ability of Java language and applications. The learning, understanding and mastering of it can not only improve our skills, but also serve us. To better understand the population of object-oriented programming, concurrent programming, high-performance programming, and distributed programming, it will further involve the operating system thread model, JVM thread model, and application scenario optimization. There are too many materials on multi-threading in the market. The PDF I want to introduce to you today is a document carefully written by an Alibaba. It can be said that it can allow you to expand your programming ability more comprehensively, and further enrich programming design and Systematic thinking of architecture design. If you have a friend who needs a high-definition PDF, like the article , follow me and add the assistant at the end of the article to get it for free , and I will show you a set of concurrent programming notes later, I hope it can be helpful to everyone!
Detailed Java High Concurrency Programming-Multithreading and Architecture Design
Catalog overview:
The first part mainly elaborates the basic knowledge of Thread, and introduces in detail the use of thread API, thread safety, data communication between threads, and how to protect shared resources. It is the basis for in-depth study of multi-threaded content.
The second part introduces ClassLoader.
In the third part, an in-depth introduction to the semantics of the volatile keyword. The volatile keyword is very important in Java. It can be said that it establishes the efficient operation of the Java core concurrent package. In this part, we show how to use the volatile key through examples. It also introduces the Java memory model and other knowledge in great detail.
The fourth part explains how to design efficient and flexible multi-threaded applications from the perspective of program architecture design
Speaking of multi-threading, we have to mention concurrent programming. Multi-threading is a way to achieve concurrency. At present, some companies always like to ask questions about the difference and connection between multi-threaded programming and concurrent programming. Many people are stupid and unclear. The following is You will show a set of concurrent programming notes, and you will know what the differences and connections are after reading it. (Due to the length of the full display, only the main content will be shown for your reference)
Concurrent programming:
principle:
mode:
application:
Write at the end
If you read the document shown above, you will know that the meaning of concurrency is actually very simple, that is, multiple people do one thing at the same time. Take a life example, when entering a subway station in the morning rush hour, a group of people rushing into the station can be considered It is a kind of concurrency, and they have to do the same thing: pit in. So what is multithreading? If one gate of a subway station is considered to be a thread, then opening multiple gates can be considered as multithreading. Of course, multi-threading is not necessarily only used in concurrency. Multi-threading is mainly to avoid that one thread is overloaded and affecting efficiency. Multi-threading can also intercept a single task into multiple segments at the same time. In this case, multi-threading is not for processing concurrency. It is like planting trees on Arbor Day. Each person is equivalent to one thread, and many people are equivalent to multiple threads. Everyone planting trees at the same time is just to improve efficiency. (Information and organized for everyone)
Since there is no xmind software on the computer now, this is the form (dog head)
If you have any doubts and puzzles in the process of learning concurrent programming, then these two documents will definitely help you to some extent. If you have a friend who needs it, just like the article, follow me and add the assistant. Available for free.
