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This article mainly explains "how to understand Java multithreading", interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let Xiaobian take you to learn "how to understand Java multithreading"!

1.1. Multithreading Basics What are threads and processes? Thread and process relationship, differences and advantages and disadvantages?

What is the difference between concurrent and parallel?

Why multithreading?

What are the possible problems with multithreading? (memory leaks, deadlocks, thread insecurity, etc.)

How many ways to create threads? (a. Inherit Thread class;b. Implement Runnable interface;c. using the Executor framework;d. using FutureTask)

What about thread life cycle and state?

What is context switching?

What is thread deadlock? How to avoid deadlock?

What is the difference between sleep() and wait() methods?

Why do we execute the run() method when we call the start() method, and why can't we call the run() method directly?

1.2. Multithreading knowledge Advanced volatile keywords

Java Memory Model (JMM);

Do you understand reordering and happens-before principles?

The role of the volatile keyword;

What is the difference between the synchronized keyword and the volatile keyword?

ThreadLocal

What's the use (what problem has been solved)? How do you use it?

Do you understand the principle?

Do you understand the memory leak problem?

thread pool

Why use thread pools?

Do you use thread pools?

How to create a thread pool is better? (ThreadPoolExecutor constructor is recommended for thread pool creation)

Do you know the important parameters of ThreadPoolExecutor class? ThreadPoolExecutor saturation strategy understand?

Do you understand thread pool theory?

Do you know some common thread pools? Why is FixedThreadPool not recommended?

How do I set the size of the thread pool?

AQS

profile

principle

AQS common components.

Semaphore-Allows simultaneous access by multiple threads

CountDownLatch-CountDownLatch allows count threads to block in one place until all threads have completed their tasks.

CyclicBarrier-CyclicBarrier is very similar to CountDownLatch in that it can also implement inter-thread technical waiting, but its functionality is more complex and powerful than CountDownLatch. The main application scenario is similar to CountDownLatch.

ReentrantLock and ReentrantReadWriteLock

lock

Common categories of locks

Reentrant and non-reentrant locks

Fair lock and unfair lock

Read-write lock and exclusive lock

synchronized keyword

Tell me about your understanding of the synchronized keyword.

Tell me how you use the synchronized keyword, is it used in the project?

Talk about the underlying principle of synchronized keyword;

Talk about JDK1.6 after synchronized keyword bottom do what optimization, can you describe these optimizations in detail?

Difference between synchronized and reentrantLock.

ReentrantLock and ReentrantReadWriteLock

ReadWriteLock

StampedLock(JDK8)

Atomic and CAS

CAS:

introduced

principle

Atomic atomic class:

Introduce the Atomic class;

What are the four atomic classes in the JUC package?

The use of AtomicInteger;

Can you give me a brief introduction to AtomicInteger class principle?

concurrent container

Most of these containers provided by JDK are in the java.util.concurrent package.

ConcurrentHashMap: Thread Safe HashMap

CopyOnWriteArrayList: Thread-safe List, which performs well in read and write situations, far better than Vector.

ConcurrentLinkedQueue: Efficient concurrency queue, implemented using linked lists. Think of it as a thread-safe LinkedList, a non-blocking queue.

BlockingQueue: This is an interface that is implemented internally by JDK through linked lists, arrays, etc. Represents a blocking queue, ideal for use as a channel for data sharing.

ConcurrentSkipListMap: Implementation of SkipListMap. This is a Map that uses a jump table data structure for quick lookups.

At this point, I believe everyone has a deeper understanding of "how to understand Java multithreading," so let's actually operate it! Here is the website, more related content can enter the relevant channels for inquiry, pay attention to us, continue to learn!

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