Shulou(Shulou.com)06/02 Report--

Today, the editor will share with you the relevant knowledge points of the common multithreaded interview questions in the Java interview. The content is detailed and the logic is clear. I believe most people still know too much about this knowledge, so share this article for your reference. I hope you can get something after reading this article. Let's take a look at it.

1. What is the difference between processes and threads

In short, a process is the basic unit of program running and resource allocation. A program has at least one process and a process has at least one thread. The process has independent memory units during execution, while multiple threads share memory resources, which reduces the number of switches and is more efficient. A thread is an entity of a process, the basic unit of cpu scheduling and dispatch, and a smaller basic unit that can run independently than a program. Multiple threads in the same process can execute concurrently.

2. What is the difference between daemon thread and non-daemon thread

When the program is finished, jvm waits for the non-daemon thread to complete and shuts down, but jvm does not wait for the daemon thread. The most typical example of a daemon thread is the GC thread

3. What is multithreaded context switching

Multi-threaded context switching refers to the process of switching CPU control from one running thread to another thread that is ready and waiting for CPU execution rights.

4. How to detect whether a thread holds an object monitor

The Thread class provides a holdsLock (Object obj) method that returns true if and only if the monitor of the object obj is held by a thread. Note that this is a static method, which means that "some thread" refers to the current thread.

5. How to wake up a blocked thread

If the thread is blocked by a call to the wait (), sleep (), or join () method, you can interrupt the thread and wake it up by throwing an InterruptedException; if the thread encounters an IO block, there is nothing you can do because the IO is implemented by the operating system, and the Java code has no way of directly touching the operating system.

6. What if a thread has a run-time exception?

If the exception is not caught, the thread stops execution. Another important point is that if the thread holds an object's monitor, the object monitor will be released immediately.

7. How to share data between two threads

You can do this by sharing objects between threads, and then evoking and waiting through wait/notify/notifyAll and await/signal/signalAll. For example, the blocking queue BlockingQueue is designed to share data between threads.

8. Why use thread pools

Avoid creating and destroying threads frequently to achieve the reuse of thread objects. In addition, using the thread pool gives you the flexibility to control the number of concurrency based on the project.

Through multithreading technology, we can make better use of system resources, make full use of the idle time of CPU, and respond to the requirements of users with as little time as possible, thus making the overall running efficiency of the process higher. For enterprises, higher operating efficiency can greatly improve the competitiveness of their own products. Therefore, the scope of application of multithreading is very wide, for Java development engineers, they must master the knowledge related to multithreading.

These are all the contents of the article "what are the common multithreaded interview questions in Java interviews?" Thank you for reading! I believe you will gain a lot after reading this article. The editor will update different knowledge for you every day. If you want to learn more knowledge, please pay attention to the industry information channel.

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