The era of mobile, 5G and Internet of Things has begun. The new era has raised the requirements for high performance and high concurrency of Java applications, and also raised the technical level and interview threshold of Java engineers. In many companies, the interview questions reflect the technical requirements of the production scenario from one side. Previously only large companies such as BAT had high concurrency technology related interview questions, but now the entire industry related to Java projects basically has such interview questions. Multi-threading, thread pool, built-in lock, JMM, CAS, JUC, high concurrency design mode and other Concurrent programming in Java interview questions, from the previous bonus questions into the now basic questions. This article focuses on the basic knowledge of Java concurrent programming and reveals the core problems and solutions of Java high concurrent programming.
The following contents are necessary knowledge for developing Java applications with high concurrency, and Java engineers must master the basic knowledge of high concurrency. Whether you are interested in Java programming college students, Java engineers, Java architects can have a look!
Due to the length problem, this article is presented in the form of pictures (mainly because I am too lazy to type, ha ha ha). If you need the original study, you can get it directly at the end of the article!
Chapter 1 introduces the core principle of thread, the basic operation of thread, the core principle of thread pool, the thread pool architecture of JUC, and four quick ways to create thread pool. In addition, the paper also describes how to estimate the number of threads in three types of thread pools (IO intensive, CPU intensive, and mixed) in production scenarios.
Chapter 2 introduces thread safety issues and the core principles of Java built-in locks based on a practical case study of the producer-consumer pattern. First, the storage layout of Java objects, the concrete structure of object headers, and how to view the structure of objects with the JOL tool. Then it introduces the core principle of synchronized internal lock and the upgrading process from partial lock to lightweight lock and then to heavyweight lock.
Chapter 3 introduces CAS principles and JUC atomic classes, and deciphers how to improve the performance of high-CAS operations in high-concurrency scenarios with intense contention. Finally, the malpractice of CAS operation and two kinds of regulation avoidance measures are revealed.
Chapter 4 introduces the three problems of concurrent programming in Java — atomicity, visibility, and order, explains the core principles of JMM, and reveals the basic knowledge of Java memory visibility and the volatile keyword.
Chapter 5 introduces the principle and practice of JUC explicit lock. This paper first introduces the correct way to use explicit lock and the classification of explicit lock, then reveals the “bus storm” and CLH spin lock that CAS may cause, and finally introduces interruptible lock and uninterruptible lock, shared lock and exclusive lock, read and write lock in JUC from examples.
Chapter 6 introduces the core principles of JUC’s high-concurrency infrastructure, the AQS Abstract synchronizer. This chapter starts from the template mode, and reveals the internal structure of AQS. Then combined with SimpleMockLock exclusive lock release process, ReentrantLock grab lock process, illustrated to analyze the release, preemption AQS lock source and principle.
Chapter 7 covers the JUC container class, including the principle and use of CopyOnWriteArrayList, BlockingQueue, ConcurrentHashMap and other high-concurrency container classes.
Chapter 8 introduces high-concurrency design patterns, including the security singleton, master-worker, ForkJoin, producer-consumer, and Future that Java development must Master.
Chapter 9 focuses on the asynchronous callback pattern, a high-concurrency design pattern often used in high-concurrency programming.
Chapter 10 describes the principles and use of the CompletableFuture class, a new utility class provided with Java 8 with asynchronous callback capabilities.
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Java high concurrency core programming documentation
