Java通过Executors框架提供四种线程池
{

        /**创建一个可缓存线程池，如果线程池长度超过处理需要，可灵活回收空闲线程，若无可回收，则新建线程。*/
        ExecutorService executorService= Executors.newCachedThreadPool();

        for (int i=0;i<10;i++)
        {
            final int index=i;
            executorService.execute(new Runnable() {
                @Override
                public void run() {
                    System.out.println(index);
                }
            });

        }

    }

{
        /**创建一个定长线程池，可控制线程最大并发数，超出的线程会在队列中等待。**/
        ExecutorService service= Executors.newFixedThreadPool(2);
        for (int i = 0; i <10 ; i++) {
            final int  index=i;
            service.execute(new Runnable() {
                @Override
                public void run() {
                    try {
                        System.out.println(index);
                        Thread.sleep(2000);
                    }catch (Exception e ){
                        System.out.println(e.getMessage());
                    }
                }
            });
        }
    }

	{


    public static void main(String[] args) {
        /**创建一个定长线程池，支持定时及周期性任务执行**/
        testOne();
        testTwo();

    }

    public static  void testOne(){
        /**表示延迟3秒执行。*/
        ScheduledExecutorService scheduledExecutorService= Executors.newScheduledThreadPool(2);
        scheduledExecutorService.schedule(new Runnable() {
            @Override
            public void run() {
                System.out.println("delay 2 seconds");
            }
        },2, TimeUnit.SECONDS);
    }

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

{
        /**
         创建一个单线程化的线程池，它只会用唯一的工作线程来执行任务，保证所有任务按照指定顺序(FIFO, LIFO, 优先级)执行**/
        ExecutorService executorService= Executors.newSingleThreadExecutor();
        for (int i = 0; i <10 ; i++) {

                final int index = i;
                executorService.execute(new Runnable() {
                    @Override
                    public void run() {
                        try {
                            Thread.sleep(2000);
                            System.out.println(index);
                            }catch(Exception e){
                                e.getMessage();
                         }
                        }
                });

        }
    }

线程池里面做了些啥 ，JDK是有工具可以查看 jconsole  在JDK的bin目录下

程序在JDK中运行后的监控



技术原理都差不多 多做记录 多学习

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

/**
 * Executors 线程池学习
 *      线程池的思想还是一种对象池的思想、开辟一块内存空间来管理众多的未死亡的线程，
 *      池中的线程调度由线程池来管理。当线程有任务的时候从线程中取出一个进行任务，完成以后归还给对象池，
 *      这样可以避免反复的创建线程对象所带来的性能开销，节省资源。
 */
public class Main {
    public static void main(String[] args) {
        //创建一个可重用固定线程数的线程池
        //ExecutorService pools = Executors.newFixedThreadPool(5);  //固定大小的任务线程池
        //ExecutorService pools = Executors.newSingleThreadExecutor(); //单任务线程池

        //ExecutorService pools = Executors.newCachedThreadPool(); //可变尺寸线程池
        ScheduledExecutorService pools = Executors.newScheduledThreadPool(2);//延迟连接池
        //创建线程
        MyThread t1 = new MyThread();
        MyThread t2 = new MyThread();
        MyThread t3 = new MyThread();
       // MyThread t4 = new MyThread();
        //MyThread t5 = new MyThread();

        //将线程放入池中进行执行
        pools.execute(t1);
        //pools.execute(t2);
        //pools.execute(t3);
        //pools.execute(t4);
        //pools.execute(t5);

        //使用延迟执行的方法风格
        pools.schedule(t2,1000, TimeUnit.MILLISECONDS);
        pools.schedule(t3,10,TimeUnit.MILLISECONDS);
        //关闭线程池
        pools.shutdown();

    }
}

1. 类 Executors 
此类中提供的一些方法有： 
1.1 public static ExecutorService newCachedThreadPool() 
创建一个可根据需要创建新线程的线程池，但是在以前构造的线程可用时将重用它们。对于执行很多短期异步任务的程序而言，这些线程池通常可提高程序性能。 

1.2 public static ExecutorService newFixedThreadPool(int nThreads) 
创建一个可重用固定线程数的线程池，以共享的无界队列方式来运行这些线程。 

1.3 public static ExecutorService newSingleThreadExecutor() 
创建一个使用单个 worker 线程的 Executor，以无界队列方式来运行该线程。 

这三个方法都可以配合接口ThreadFactory的实例一起使用。并且返回一个ExecutorService接口的实例。 
2. 接口 ThreadFactory 
根据需要创建新线程的对象。使用线程工厂就无需再手工编写对 new Thread 的调用了，从而允许应用程序使用特殊的线程子类、属性等等。 
此接口最简单的实现就是： 


Java代码  


class SimpleThreadFactory implements ThreadFactory {  
   public Thread newThread(Runnable r) {  
     return new Thread(r);  
   }  
 }  


3. 接口ExecutorService 
该接口提供了管理终止的方法。 
4.创建标准线程池启动线程 
4.1 提供一个简单的实现Runnable接口的线程 
MyThread.java 


Java代码  


package com.zj.concurrency.executors;  
   
public class MyThread implements Runnable {  
    private int count = 1, number;  
   
    public MyThread(int num) {  
       number = num;  
       System.out.println("Create Thread-" + number);  
    }  
   
    public void run() {  
       while (true) {  
           System.out.println("Thread-" + number + " run " + count+" time(s)");  
           if (++count == 3)  
              return;  
       }  
    }  
}  


这个线程会打印出相应的创建和执行信息。 

4.2使用CachedThreadPool启动线程 
CachedThreadPool.java 


Java代码  


package com.zj.concurrency.executors;  
import java.util.concurrent.ExecutorService;  
import java.util.concurrent.Executors;  
   
public class CachedThreadPool {  
    public static void main(String[] args) {  
       ExecutorService exec = Executors.newCachedThreadPool();  
       for (int i = 0; i < 5; i++)  
           exec.execute(new MyThread(i));  
       exec.shutdown();  
    }  
}  


结果： 
Create Thread-0 
Create Thread-1 
Create Thread-2 
Create Thread-3 
Thread-0 run 1 time(s) 
Thread-0 run 2 time(s) 
Thread-1 run 1 time(s) 
Thread-1 run 2 time(s) 
Thread-2 run 1 time(s) 
Thread-2 run 2 time(s) 
Create Thread-4 
Thread-4 run 1 time(s) 
Thread-4 run 2 time(s) 
Thread-3 run 1 time(s) 
Thread-3 run 2 time(s) 

4.3 使用FixedThreadPool启动线程 
FixedThreadPool.java 


Java代码  


package com.zj.concurrency.executors;  
import java.util.concurrent.ExecutorService;  
import java.util.concurrent.Executors;  
   
public class FixedThreadPool {  
    public static void main(String[] args) {  
       ExecutorService exec = Executors.newFixedThreadPool(2);  
       for (int i = 0; i < 5; i++)  
           exec.execute(new MyThread(i));  
       exec.shutdown();  
    }  
}  


结果： 
Create Thread-0 
Create Thread-1 
Create Thread-2 
Create Thread-3 
Create Thread-4 
Thread-0 run 1 time(s) 
Thread-0 run 2 time(s) 
Thread-2 run 1 time(s) 
Thread-2 run 2 time(s) 
Thread-3 run 1 time(s) 
Thread-3 run 2 time(s) 
Thread-4 run 1 time(s) 
Thread-4 run 2 time(s) 
Thread-1 run 1 time(s) 
Thread-1 run 2 time(s) 

4.4 使用SingleThreadExecutor启动线程 
SingleThreadExecutor.java 


Java代码  


package com.zj.concurrency.executors;  
import java.util.concurrent.ExecutorService;  
import java.util.concurrent.Executors;  
   
public class SingleThreadExecutor {  
    public static void main(String[] args) {  
       ExecutorService exec = Executors.newSingleThreadExecutor();  
       for (int i = 0; i < 5; i++)  
           exec.execute(new MyThread(i));  
       exec.shutdown();  
    }  
}  


结果： 
Create Thread-0 
Create Thread-1 
Create Thread-2 
Create Thread-3 
Create Thread-4 
Thread-0 run 1 time(s) 
Thread-0 run 2 time(s) 
Thread-1 run 1 time(s) 
Thread-1 run 2 time(s) 
Thread-2 run 1 time(s) 
Thread-2 run 2 time(s) 
Thread-3 run 1 time(s) 
Thread-3 run 2 time(s) 
Thread-4 run 1 time(s) 
Thread-4 run 2 time(s) 
5.配合ThreadFactory接口的使用 
我们试图给线程加入daemon和priority的属性设置。 
5.1设置后台线程属性 
DaemonThreadFactory.java 


Java代码  


package com.zj.concurrency.executors.factory;  
import java.util.concurrent.ThreadFactory;  
   
public class DaemonThreadFactory implements ThreadFactory {  
    public Thread newThread(Runnable r) {  
       Thread t = new Thread(r);  
       t.setDaemon(true);  
       return t;  
    }  
}  



5.2 设置优先级属性 
最高优先级MaxPriorityThreadFactory.java 


Java代码  


package com.zj.concurrency.executors.factory;  
import java.util.concurrent.ThreadFactory;  
   
public class MaxPriorityThreadFactory implements ThreadFactory {  
    public Thread newThread(Runnable r) {  
       Thread t = new Thread(r);  
       t.setPriority(Thread.MAX_PRIORITY);  
       return t;  
    }  
}  


最低优先级MinPriorityThreadFactory.java 


Java代码  


package com.zj.concurrency.executors.factory;  
import java.util.concurrent.ThreadFactory;  
   
public class MinPriorityThreadFactory implements ThreadFactory {  
    public Thread newThread(Runnable r) {  
       Thread t = new Thread(r);  
       t.setPriority(Thread.MIN_PRIORITY);  
       return t;  
    }  
}  



5.3启动带有属性设置的线程 
ExecFromFactory.java 


Java代码  


package com.zj.concurrency.executors;  
import java.util.concurrent.ExecutorService;  
import java.util.concurrent.Executors;  
import com.zj.concurrency.executors.factory.DaemonThreadFactory;  
import com.zj.concurrency.executors.factory.MaxPriorityThreadFactory;  
import com.zj.concurrency.executors.factory.MinPriorityThreadFactory;  
   
public class ExecFromFactory {  
    public static void main(String[] args) throws Exception {  
       ExecutorService defaultExec = Executors.newCachedThreadPool();  
       ExecutorService daemonExec = Executors  
              .newCachedThreadPool(new DaemonThreadFactory());  
       ExecutorService maxPriorityExec = Executors  
              .newCachedThreadPool(new MaxPriorityThreadFactory());  
       ExecutorService minPriorityExec = Executors  
              .newCachedThreadPool(new MinPriorityThreadFactory());  

配置：以进程或线程方式执行任务
1.以线程执行任务
from apscheduler.executors.pool import ThreadPoolExecutor

executors = {
    'default': ThreadPoolExecutor(20) #最多20个线程同时执行
}
scheduler = BackgroundScheduler(executors=executors)

2.以进程方式执行任务
from apscheduler.executors.pool import ProcessPoolExecutor
executors = {
    'default': ProcessPoolExecutor(3) #最多3个进程同时执行
}
scheduler = BackgroundScheduler(executors=executors)