Several common thread pools in Java

Several common thread pools in Java

Reprint: https://www.cnblogs.com/sachen/p/7401959.html

original April 14, 2016 23:29:01

• Label:
• Java/
• Thread pool/
• Executor

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Overview:

The class used to manipulate threads in the Java built-in API is thread. There are generally two ways to create a thread,

• Inherit thread mode

• Implement runnable mode and create thread with runnable as target

Time-consuming tasks in Android typically require a separate thread to execute, often using a pool of threads to manage the number of threads, reuse, control execution, and cancellation.

Java thread pool

Java provides four thread pools

Newcachedthreadpool:

The thread pool can be cached, if the thread pool length exceeds the processing needs, then the empty thread is reclaimed, otherwise a new thread is created, and the size of the threads can be infinitely large.

ExecutorService cachedThreadPool = Executors.newCachedThreadPool();

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When the first task is completed while performing the second task, the thread that executes the first task is reused instead of each new thread.

Newfixedthreadpool:

The thread pool, which controls the maximum number of concurrent threads, waits in the queue for the exceeded thread.

ExecutorService fixedThreadPool = Executors.newFixedThreadPool(3);

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The size of a fixed-length pool is best set based on system resources. such as Runtime.getruntime (). Availableprocessors ().

Newscheduledthreadpool:

Fixed-line pool, support timing and periodic task execution, similar to timer.

ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(5);

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Usage examples:

ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(5);//表示延迟1秒后每3秒执行一次。scheduledThreadPool.scheduleAtFixedRate(new Runnable() {    @Override    public void run() { System.out.println("delay 1 seconds, and excute every 3 seconds"); }}, 1, 3, TimeUnit.SECONDS);

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Newsinglethreadexecutor:

Single thread pool, support FIFO, LIFO, priority policy.

ExecutorService singleThreadExecutor = Executors.newSingleThreadExecutor();

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By observing the source code, four of these threads are created to create a threadpoolexecutor. Where Threadpoolexecutor is the implementation class for the Executorservice interface.

Java.util.concurrent

This package is Java's concurrent programming package, which defines three executor interfaces

Executor: A simple interface to run a new task.
Executorservice: extended the Executor interface. Added some methods to manage the life cycle of the executor and the life cycle of the task.
Scheduledexecutorservice: Extended the Executorservice. Support Future and perform tasks on a regular basis.

Implementation classes include: Scheduledthreadpoolexecutor, Threadpoolexecutor.
The four thread pools available in Java, in addition to Scheduledthreadpool, use Scheduledthreadpoolexecutor, others are threadpoolexecutor.

Threadpoolexecutor

public ThreadPoolExecutor(int corePoolSize,                              int maximumPoolSize,                              long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory, RejectedExecutionHandler handler) {}

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Parameter description
Corepoolsize: The number of core threads for the thread pool.
Maximumpoolsize: The maximum number of threads that the thread pool can hold.
KeepAliveTime: The timeout length when non-core threads are idle. Beyond that time, non-core threads are recycled.
The time unit of the unit:keepalivetime.
WorkQueue: The task queue in the thread pool.
Threadfactory: Thread factory, default value defaultthreadfactory.
Handler: Saturation policy, when the number of thread pools is greater than maximumpoolsize, the processing policy for the rejected task, the default value Threadpoolexecutor.abortpolicy ().

Reference:
Java Concurrency Tutorial (Oracle official profile)

Trinea:java (Android) thread pool

Java Multithreading: Threadpoolexecutor detailed

Concurrent Programming Network-ifeve.com

Thread Pool Threadpoolexecutor Introduction

Several common thread pools in Java