ThreadPoolExecutor threadPoolExecutor=new ThreadPoolExecutor (
int corePoolSize,
int maximumPoolSize ,
long keepAliveTime ,
TimeUnit unit,
BlockingQueue<Runnable> workQueue,
 ThreadFactory threadFactory,
 RejectedExecutionHandler handler
 )

 ExecutorService Service1   =  Executors.newFixedThreadPool (20);

ExecutorService Service2   = Executors.newCachedThreadPool ();

ExecutorService Service3  = Executors.newSingleThreadExecutor ();

ExecutorService Service4   = Executors.newScheduledThreadPool (20);

模擬實(shí)現(xiàn)一個(gè)線程池的核心操作：
.:將任務(wù)加到線程池中--submit。
.:使用Worker類描述一個(gè)工作線程，Runnable來(lái)描述一個(gè)任務(wù)。
.:創(chuàng)建一個(gè)BlockingQueue阻塞隊(duì)列組織所有任務(wù)。
.:每個(gè)Worker要做的事情就是不停的從阻塞隊(duì)列里獲取任務(wù)并執(zhí)行。
.:指定線程池中的線程最大數(shù)目，如果超過(guò)這個(gè)數(shù)目就不要再繼續(xù)創(chuàng)建線程了。

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;

/**
 * Created with IntelliJ IDEA.
 *
 
 * @Description: 模擬實(shí)現(xiàn)線程池的使用
 */
public class ThreadDemo0327_2 {
    public static void main (String[] args) throws IOException, InterruptedException {
        ThreadPoll threadPoll=new ThreadPoll ();
        for (int i = 0 ; i <10  ; i++) {
            threadPoll.submit (new Runnable () {
                @Override
                public void run () {
                    System.out.println ("hello");
                }
            });
        }
    }
}

class  Worker extends  Thread{
    public   BlockingQueue<Runnable> queue=null;
    public Worker(BlockingQueue<Runnable> queue){
        this.queue=queue;
    }

    @Override
    public void run () {
        //工作線程的具體邏輯
        //需要從阻塞隊(duì)列中取任務(wù).
        while (true){
            try {
                Runnable command=queue.take ();
                //通過(guò)run來(lái)執(zhí)行具體任務(wù)
                command.run ();
            }catch (InterruptedException e){
                e.printStackTrace ();
            }
        }
    }
}

class  ThreadPoll{
    //包含一個(gè)阻塞隊(duì)列，用來(lái)組織任務(wù)
  public   BlockingQueue<Runnable> queue=new LinkedBlockingQueue<> ();

    //這個(gè)list就用來(lái)存放當(dāng)前的工作線程.
    public  List<Thread> works=new ArrayList<> ();

    public  int MAX_WORKER_COUNT=10;

    //通過(guò)這個(gè)方法，把任務(wù)加入到線程池中
    //submit不光可以把任務(wù)放到阻塞隊(duì)列中，也可以負(fù)責(zé)創(chuàng)建線程
    public  void submit(Runnable command) throws IOException, InterruptedException {
        if(works.size ()<MAX_WORKER_COUNT){
            //如果當(dāng)前工作線程的數(shù)量不足線程數(shù)目上線，就創(chuàng)建出新的線程
            //工作線程就專門找一個(gè)類完成
            //worker內(nèi)部要哦能夠取到隊(duì)列的內(nèi)容，就要把這個(gè)隊(duì)列實(shí)例通過(guò)worker的構(gòu)造方法傳過(guò)去
            Worker worker=new Worker (queue);
            worker.start ();
            works.add (worker);
        }
        queue.put (command);
    }
}