重庆网站搜索排名,网站推广app,猪八戒里面做网站骗子很多,wordpress 多站点设置线程池管理工作线程池#xff0c;它包含一个队列#xff0c;使任务等待执行。 线程池管理可运行线程的集合#xff0c;工作线程从队列中执行可运行线程。 java.util.concurrent.Executors提供java.util.concurrent.Executor接口的实现#xff0c;以在Java中创建线程池。 让… 线程池管理工作线程池它包含一个队列使任务等待执行。 线程池管理可运行线程的集合工作线程从队列中执行可运行线程。 java.util.concurrent.Executors提供java.util.concurrent.Executor接口的实现以在Java中创建线程池。 让我们编写一个简单的程序来说明它的工作原理。 首先我们需要有一个Runnable类。 package com.journaldev.threadpool;public class WorkerThread implements Runnable {private String command;public WorkerThread(String s){this.commands;}Overridepublic void run() {System.out.println(Thread.currentThread().getName() Start. Command command);processCommand();System.out.println(Thread.currentThread().getName() End.);}private void processCommand() {try {Thread.sleep(5000);} catch (InterruptedException e) {e.printStackTrace();}}Overridepublic String toString(){return this.command;}
} 这是我们从Executors框架创建固定线程池的测试程序。 package com.journaldev.threadpool;import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;public class SimpleThreadPool {public static void main(String[] args) {ExecutorService executor Executors.newFixedThreadPool(5);for (int i 0; i 10; i) {Runnable worker new WorkerThread( i);executor.execute(worker);}executor.shutdown();while (!executor.isTerminated()) {}System.out.println(Finished all threads);}} 在上面的程序中我们正在创建5个工作线程的固定大小的线程池。 然后我们将10个作业提交到该池中因为该池的大小为5它将开始处理5个作业其他作业将处于等待状态一旦其中一个作业完成来自等待队列的另一个作业将被工作线程拾取并执行。 这是上面程序的输出。 pool-1-thread-2 Start. Command 1
pool-1-thread-4 Start. Command 3
pool-1-thread-1 Start. Command 0
pool-1-thread-3 Start. Command 2
pool-1-thread-5 Start. Command 4
pool-1-thread-4 End.
pool-1-thread-5 End.
pool-1-thread-1 End.
pool-1-thread-3 End.
pool-1-thread-3 Start. Command 8
pool-1-thread-2 End.
pool-1-thread-2 Start. Command 9
pool-1-thread-1 Start. Command 7
pool-1-thread-5 Start. Command 6
pool-1-thread-4 Start. Command 5
pool-1-thread-2 End.
pool-1-thread-4 End.
pool-1-thread-3 End.
pool-1-thread-5 End.
pool-1-thread-1 End.
Finished all threads 输出确认池中有五个线程来自“ pool-1-thread-1 到“ pool-1-thread-5” 他们负责执行提交给池的任务。 Executors类提供简单实现的ExecutorService的使用的ThreadPoolExecutor但ThreadPoolExecutor的提供了更多的功能不止于此。 我们可以指定创建ThreadPoolExecutor实例时仍处于活动状态的线程数并且可以限制线程池的大小并创建自己的RejectedExecutionHandler实现以处理无法容纳在工作队列中的作业。 这是我们对RejectedExecutionHandler接口的自定义实现。 package com.journaldev.threadpool;import java.util.concurrent.RejectedExecutionHandler;
import java.util.concurrent.ThreadPoolExecutor;public class RejectedExecutionHandlerImpl implements RejectedExecutionHandler {Overridepublic void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {System.out.println(r.toString() is rejected);}} ThreadPoolExecutor提供了几种方法通过这些方法我们可以找到执行器的当前状态池大小活动线程数和任务数。 因此我有一个监视线程它将在特定时间间隔打印执行程序信息。 package com.journaldev.threadpool;import java.util.concurrent.ThreadPoolExecutor;public class MyMonitorThread implements Runnable
{private ThreadPoolExecutor executor;private int seconds;private boolean runtrue;public MyMonitorThread(ThreadPoolExecutor executor, int delay){this.executor executor;this.secondsdelay;}public void shutdown(){this.runfalse;}Overridepublic void run(){while(run){System.out.println(String.format([monitor] [%d/%d] Active: %d, Completed: %d, Task: %d, isShutdown: %s, isTerminated: %s,this.executor.getPoolSize(),this.executor.getCorePoolSize(),this.executor.getActiveCount(),this.executor.getCompletedTaskCount(),this.executor.getTaskCount(),this.executor.isShutdown(),this.executor.isTerminated()));try {Thread.sleep(seconds*1000);} catch (InterruptedException e) {e.printStackTrace();}}}
} 这是使用ThreadPoolExecutor的线程池实现示例。 package com.journaldev.threadpool;import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;public class WorkerPool {public static void main(String args[]) throws InterruptedException{//RejectedExecutionHandler implementationRejectedExecutionHandlerImpl rejectionHandler new RejectedExecutionHandlerImpl();//Get the ThreadFactory implementation to useThreadFactory threadFactory Executors.defaultThreadFactory();//creating the ThreadPoolExecutorThreadPoolExecutor executorPool new ThreadPoolExecutor(2, 4, 10, TimeUnit.SECONDS, new ArrayBlockingQueueRunnable(2), threadFactory, rejectionHandler);//start the monitoring threadMyMonitorThread monitor new MyMonitorThread(executorPool, 3);Thread monitorThread new Thread(monitor);monitorThread.start();//submit work to the thread poolfor(int i0; i10; i){executorPool.execute(new WorkerThread(cmdi));}Thread.sleep(30000);//shut down the poolexecutorPool.shutdown();//shut down the monitor threadThread.sleep(5000);monitor.shutdown();}
} 请注意在初始化ThreadPoolExecutor时我们将初始池大小保持为2最大池大小保持为4工作队列大小保持为2。因此如果有4个正在运行的任务并且提交了更多任务则工作队列将仅容纳其中2个其余的将由RejectedExecutionHandlerImpl处理。 这是上述程序的输出确认上述声明。 pool-1-thread-1 Start. Command cmd0
pool-1-thread-4 Start. Command cmd5
cmd6 is rejected
pool-1-thread-3 Start. Command cmd4
pool-1-thread-2 Start. Command cmd1
cmd7 is rejected
cmd8 is rejected
cmd9 is rejected
[monitor] [0/2] Active: 4, Completed: 0, Task: 6, isShutdown: false, isTerminated: false
[monitor] [4/2] Active: 4, Completed: 0, Task: 6, isShutdown: false, isTerminated: false
pool-1-thread-4 End.
pool-1-thread-1 End.
pool-1-thread-2 End.
pool-1-thread-3 End.
pool-1-thread-1 Start. Command cmd3
pool-1-thread-4 Start. Command cmd2
[monitor] [4/2] Active: 2, Completed: 4, Task: 6, isShutdown: false, isTerminated: false
[monitor] [4/2] Active: 2, Completed: 4, Task: 6, isShutdown: false, isTerminated: false
pool-1-thread-1 End.
pool-1-thread-4 End.
[monitor] [4/2] Active: 0, Completed: 6, Task: 6, isShutdown: false, isTerminated: false
[monitor] [2/2] Active: 0, Completed: 6, Task: 6, isShutdown: false, isTerminated: false
[monitor] [2/2] Active: 0, Completed: 6, Task: 6, isShutdown: false, isTerminated: false
[monitor] [2/2] Active: 0, Completed: 6, Task: 6, isShutdown: false, isTerminated: false
[monitor] [2/2] Active: 0, Completed: 6, Task: 6, isShutdown: false, isTerminated: false
[monitor] [2/2] Active: 0, Completed: 6, Task: 6, isShutdown: false, isTerminated: false
[monitor] [0/2] Active: 0, Completed: 6, Task: 6, isShutdown: true, isTerminated: true
[monitor] [0/2] Active: 0, Completed: 6, Task: 6, isShutdown: true, isTerminated: true 注意执行程序的活动已完成和已完成任务总数的变化。 我们可以调用shutdown方法来完成所有提交的任务的执行并终止线程池。 参考 Java线程池示例使用我们的JCG合作伙伴 Pankaj Kumar的Executors和ThreadPoolExecutor 位于Developer Recipes博客上。 翻译自: https://www.javacodegeeks.com/2013/01/java-thread-pool-example-using-executors-and-threadpoolexecutor.html
