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This article mainly explains "what is the thread pool of Java". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "what is the thread pool of Java".

Introduction to thread pool

The concept of thread pool:

A thread pool is to first create some threads whose collection is called a thread pool. Using the thread pool can improve performance very well. The thread pool creates a large number of idle threads when the system starts, and the program passes a task to the thread pool, and the thread pool starts a thread to execute the task. After execution, the thread does not die, but returns to the thread pool to become idle again, waiting for the next task to be executed.

How thread pools work:

In the thread pool programming mode, the task is submitted to the entire thread pool rather than directly to a thread. After getting the task, the thread pool looks internally to see if there is an idle thread, and if so, hand the task over to some idle thread.

A thread can perform only one task at a time, but can submit multiple tasks to a thread pool at the same time.

Reasons for using thread pools:

Multi-thread running time, the system constantly starts and shuts down new threads, the cost is very high, will excessive consumption of system resources, and the danger of switching threads, which may lead to the collapse of system resources. At this point, the thread pool is the best choice.

Four kinds of common thread pool detailed explanation 4.1 Executors.newCacheThreadPool ()

Executors.newCacheThreadPool (): caches the thread pool, first check to see if there are any previously established threads in the pool, and if so, use it directly. If not, build a new thread to join the pool, which is usually used to perform asynchronous tasks with a short lifetime

Code:

Import java.util.concurrent.ExecutorService

Import java.util.concurrent.Executors

Public class ThreadPoolExecutorTest {

Public static void main (String [] args) {

/ / create a cacheable thread pool

ExecutorService cachedThreadPool = Executors.newCachedThreadPool ()

For (int I = 0; I < 10; iTunes +) {

Try {

/ / sleep can clearly see that the previous thread in the thread pool is used and no new thread is created

Thread.sleep (1000)

} catch (InterruptedException e) {

E.printStackTrace ()

}

CachedThreadPool.execute (new Runnable () {

Public void run () {

/ / print the cache thread information that is being executed

System.out.println (Thread.currentThread () .getName () + "being executed")

}

});

}

}

}

The thread pool is infinite, and when the previous task is completed when the current task is executed, the thread executing the previous task is reused instead of each new thread.

4.2 Executors.newFixedThreadPool (int n)

Executors.newFixedThreadPool (int n): create a pool of reusable and fixed number of threads to run them in a shared unbounded queue.

Code:

Package com.study.test

Import java.util.concurrent.ExecutorService

Import java.util.concurrent.Executors

Public class ThreadPoolExecutorTest {

Public static void main (String [] args) {

/ / create a reusable thread pool with a fixed number

ExecutorService fixedThreadPool = Executors.newFixedThreadPool (3)

For (int I = 0; I < 10; iTunes +) {

FixedThreadPool.execute (new Runnable () {

Public void run () {

Try {

/ / print the cache thread information that is being executed

System.out.println (Thread.currentThread () .getName () + "being executed")

Thread.sleep (2000)

} catch (InterruptedException e) {

E.printStackTrace ()

}

}

});

}

}

}

}

4.3 Executors.newScheduledThreadPool (int n)

Executors.newScheduledThreadPool (int n): create a fixed-length thread pool that supports scheduled and periodic task execution

Code:

Package com.study.test

Import java.util.concurrent.Executors

Import java.util.concurrent.ScheduledExecutorService

Import java.util.concurrent.TimeUnit

Public class ThreadPoolExecutorTest {

Public static void main (String [] args) {

/ / create a fixed-length thread pool that supports scheduled and periodic task execution-delayed execution

ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool (5)

/ / delay execution by 1 second

ScheduledThreadPool.schedule (new Runnable () {

Public void run () {

System.out.println ("delay execution by 1 second")

}

}, 1, TimeUnit.SECONDS)

}

}

Output: 1 second delay in execution

Code 2: can be executed on a regular basis

Package com.study.test

Import java.util.concurrent.Executors

Import java.util.concurrent.ScheduledExecutorService

Import java.util.concurrent.TimeUnit

Public class ThreadPoolExecutorTest {

Public static void main (String [] args) {

/ / create a fixed-length thread pool that supports scheduled and periodic task execution-periodic execution

ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool (5)

/ / execute every 3 seconds after a delay of 1 second

ScheduledThreadPool.scheduleAtFixedRate (new Runnable () {

Public void run () {

System.out.println ("execute every 3 seconds after 1 second delay")

}

}, 1,3, TimeUnit.SECONDS)

}

}

4.4 Executors.newSingleThreadExecutor ()

Executors.newSingleThreadExecutor (): create a single-threaded thread pool that only uses a single worker thread to execute tasks, ensuring that all tasks are executed in a specified order (FIFO, LIFO, priority).

Package com.study.test

Import java.util.concurrent.ExecutorService

Import java.util.concurrent.Executors

Public class TestThreadPoolExecutor {

Public static void main (String [] args) {

ExecutorService singleThreadExecutor = Executors.newSingleThreadExecutor ()

For (int I = 0; I < 10; iTunes +) {

Final int index = I

SingleThreadExecutor.execute (new Runnable () {

Public void run () {

Try {

/ / the results are output in turn, which is equivalent to executing each task sequentially

System.out.println (Thread.currentThread (). GetName () + "is being executed, and the printed value is:" + index)

Thread.sleep (1000)

} catch (InterruptedException e) {

E.printStackTrace ()

}

}

});

}

}

}

Thank you for your reading, these are the contents of "what is the thread pool of Java?" after the study of this article, I believe you have a deeper understanding of what the thread pool of Java has, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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