public static void main(String[] args) throws InterruptedException {
        long start = System.currentTimeMillis();
        final List<Integer> list = new ArrayList<>();
        final Random random = new Random();
        for (int i = 0; i < 100000; i++) {
            Thread thread = new Thread() {
                @Override
                public void run() {
                    list.add(random.nextInt());
                }
            };
            thread.start();
            thread.join();
        }
        System.out.println("執(zhí)行時(shí)間:" + (System.currentTimeMillis() - start));
        System.out.println("執(zhí)行大小：" + list.size());
    }

  public static void main(String[] args) throws InterruptedException {
        long start = System.currentTimeMillis();
        final List<Integer> list = new ArrayList<>();
        final Random random = new Random();
        ExecutorService executorService = Executors.newSingleThreadExecutor();
        for (int i = 0; i < 100000; i++) {
            executorService.execute(()->{
                list.add(random.nextInt());
            });
        }
        executorService.shutdown();
        executorService.awaitTermination(1, TimeUnit.DAYS);
        System.out.println("執(zhí)行時(shí)間:" + (System.currentTimeMillis() - start));
        System.out.println("執(zhí)行大小：" + list.size());
    }

  public static ExecutorService newCachedThreadPool() {
        return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
                                      60L, TimeUnit.SECONDS,
                                      new SynchronousQueue<Runnable>());
    }

 public static ExecutorService newFixedThreadPool(int nThreads) {
        return new ThreadPoolExecutor(nThreads, nThreads,
                                      0L, TimeUnit.MILLISECONDS,
                                      new LinkedBlockingQueue<Runnable>());
    }

 public static ExecutorService newSingleThreadExecutor() {
        return new FinalizableDelegatedExecutorService
            (new ThreadPoolExecutor(1, 1,
                                    0L, TimeUnit.MILLISECONDS,
                                    new LinkedBlockingQueue<Runnable>()));
    }

public ScheduledThreadPoolExecutor(int corePoolSize) {
        super(corePoolSize, Integer.MAX_VALUE, 0, NANOSECONDS,
              new DelayedWorkQueue());
    }

 ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(10, 20,
                0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>(10),new MonkeyRejectedExecutionHandler());

public void execute(Runnable command) {
	if (command == null)
            throw new NullPointerException();
 	int c = ctl.get();
 	//1.判斷線程數(shù)是否小于核心線程數(shù)，如果是則使用入?yún)⑷蝿?wù)通過(guò)addWorker方法創(chuàng)建一個(gè)新的線程，如果能完成新線程創(chuàng)建execute方法結(jié)束，成功提交任務(wù)
    if (workerCountOf(c) < corePoolSize) {
        if (addWorker(command, true))
            return;
        c = ctl.get();
    }
    //2.在第一步?jīng)]有完成任務(wù)提交；狀態(tài)為運(yùn)行并且能成功加入任務(wù)到工作隊(duì)列后，再進(jìn)行一次check，如果狀態(tài)在任務(wù)加入隊(duì)列后變?yōu)榱朔沁\(yùn)行（有可能是在執(zhí)行到這里線程池shtdown了）,非運(yùn)行狀態(tài)下當(dāng)然是需要reject；
    // offer和add方法差不多，add方法就是調(diào)用的offer,只不過(guò)比offer多拋出一個(gè)異常 throw new IllegalStateException("Queue full")
    if (isRunning(c) && workQueue.offer(command)) {
        int recheck = ctl.get();
        if (! isRunning(recheck) && remove(command))
            reject(command);
            //3.判斷當(dāng)前工作線程池?cái)?shù)是否為0,如果是創(chuàng)建一個(gè)null任務(wù)，任務(wù)在堵塞隊(duì)列存在了就會(huì)從隊(duì)列中取出這樣做的意義是保證線程池在running狀態(tài)必須有一個(gè)任務(wù)在執(zhí)行
        else if (workerCountOf(recheck) == 0)
            addWorker(null, false);
    }
    //4.如果不能加入任務(wù)到工作隊(duì)列，將嘗試使用任務(wù)新增一個(gè)線程，如果失敗，則是線程池已經(jīng)shutdown或者線程池已經(jīng)達(dá)到飽和狀態(tài)，所以reject.拒絕策略不僅僅是在飽和狀態(tài)下使用，在線程池進(jìn)入到關(guān)閉階段同樣需要使用到；
    else if (!addWorker(command, false))
        reject(command);
 	}
}

private boolean addWorker(Runnable firstTask, boolean core) {
		// goto寫(xiě)法 重試
        retry:
        for (;;) {
            int c = ctl.get();
            int rs = runStateOf(c);
            // Check if queue empty only if necessary.
            if (rs >= SHUTDOWN &&
                ! (rs == SHUTDOWN &&
                   firstTask == null &&
                   ! workQueue.isEmpty()))
                   //線程狀態(tài)非運(yùn)行并且非shutdown狀態(tài)任務(wù)為空，隊(duì)列非空就不能新增線程了
                return false;
            for (;;) {
                int wc = workerCountOf(c);
                if (wc >= CAPACITY ||
                    wc >= (core ? corePoolSize : maximumPoolSize))
                    //當(dāng)前線程達(dá)到了最大閾值 就不再新增線程了
                    return false;
                if (compareAndIncrementWorkerCount(c))
                	//ctl+1工作線程池?cái)?shù)量+1如果成功 就跳出死循環(huán)
                    break retry;
                c = ctl.get();  // Re-read ctl
                if (runStateOf(c) != rs)
                //進(jìn)來(lái)的狀態(tài)和此時(shí)的狀態(tài)發(fā)生改變重頭開(kāi)始重試
                    continue retry;
                // else CAS failed due to workerCount change; retry inner loop
            }
        }
        boolean workerStarted = false;
        boolean workerAdded = false;
        Worker w = null;
        try {
            w = new Worker(firstTask);//內(nèi)部類封裝了線程和任務(wù) 通過(guò)threadfactory創(chuàng)建線程
            //毎一個(gè)worker就是一個(gè)線程數(shù)
            final Thread t = w.thread;
            if (t != null) {
                final ReentrantLock mainLock = this.mainLock;
                mainLock.lock();
                try {
                   //重新獲取線程狀態(tài)
                    int rs = runStateOf(ctl.get());
					// 狀態(tài)小于shutdown 就是running狀態(tài) 或者 為shutdown并且firstTask為空是從隊(duì)列中處理      任務(wù)那就可以放到集合中
                    if (rs < SHUTDOWN ||
                        (rs == SHUTDOWN && firstTask == null)) {
                       // 線程還沒(méi)start就是alive就直接異常
                        if (t.isAlive()) 
                            throw new IllegalThreadStateException();
                        workers.add(w);
                        int s = workers.size();
                        if (s > largestPoolSize)
                        // 記錄最大線程數(shù)
                            largestPoolSize = s;
                        workerAdded = true;
                    }
                } finally {
                    mainLock.unlock();
                }
                if (workerAdded) {
                    t.start();
                    workerStarted = true;
                }
            }
        } finally {
            if (! workerStarted)
            //失敗回退從wokers移除w線程數(shù)減1嘗試結(jié)束線程池
                addWorkerFailed(w);
        }
        return workerStarted;
    }

    private final class Worker
        extends AbstractQueuedSynchronizer
        implements Runnable
    {
        /**
         * This class will never be serialized, but we provide a
         * serialVersionUID to suppress a javac warning.
         */
        private static final long serialVersionUID = 6138294804551838833L;
        /** Thread this worker is running in.  Null if factory fails. */
        //正在運(yùn)行woker線程
        final Thread thread;
        /** Initial task to run.  Possibly null. */
        //傳入的任務(wù)
        Runnable firstTask;
        /** Per-thread task counter */
        //完成的任務(wù)數(shù)監(jiān)控用
        volatile long completedTasks;
        /**
         * Creates with given first task and thread from ThreadFactory.
         * @param firstTask the first task (null if none)
         */
        Worker(Runnable firstTask) {
            //禁止線程中斷
            setState(-1); // inhibit interrupts until runWorker
            this.firstTask = firstTask;
            this.thread = getThreadFactory().newThread(this);
        }
        /** Delegates main run loop to outer runWorker  */
        public void run() {
            runWorker(this);
        }

final void runWorker(Worker w) {
		//獲取當(dāng)前線程
        Thread wt = Thread.currentThread();
        Runnable task = w.firstTask;
        w.firstTask = null;
        w.unlock(); // allow interrupts 把state從‐1改為0意思是可以允許中斷
        boolean completedAbruptly = true;
        try {
        	//task不為空或者阻塞隊(duì)列中拿到了任務(wù)
            while (task != null || (task = getTask()) != null) {
                w.lock();
                // If pool is stopping, ensure thread is interrupted;
                // if not, ensure thread is not interrupted.  This
                // requires a recheck in second case to deal with
                // shutdownNow race while clearing interrupt
                //如果當(dāng)前線程池狀態(tài)等于stop就中斷
                if ((runStateAtLeast(ctl.get(), STOP) ||
                     (Thread.interrupted() &&
                      runStateAtLeast(ctl.get(), STOP))) &&
                    !wt.isInterrupted())
                    wt.interrupt();
                try {
                    beforeExecute(wt, task);
                    Throwable thrown = null;
                    try {
                        task.run();
                    } catch (RuntimeException x) {
                        thrown = x; throw x;
                    } catch (Error x) {
                        thrown = x; throw x;
                    } catch (Throwable x) {
                        thrown = x; throw new Error(x);
                    } finally {
                        afterExecute(task, thrown);
                    }
                } finally {
                  //這設(shè)置為空等下次循環(huán)就會(huì)從隊(duì)列里面獲取 
                    task = null;
                    //完成任務(wù)數(shù)+1
                    w.completedTasks++;
                    w.unlock();
                }
            }
            completedAbruptly = false;
        } finally {
            processWorkerExit(w, completedAbruptly);
        }
    }

    private Runnable getTask() {
        boolean timedOut = false; // Did the last poll() time out?
        for (;;) {
            int c = ctl.get();
            int rs = runStateOf(c);//獲取線程池運(yùn)行狀態(tài)
            // Check if queue empty only if necessary.
            //shutdown或者為空那就工作線程‐1同時(shí)返回為null
            if (rs >= SHUTDOWN && (rs >= STOP || workQueue.isEmpty())) {
                decrementWorkerCount();
                return null;
            }
			//重新獲取工作線程數(shù)
            int wc = workerCountOf(c);
            // Are workers subject to culling?
            // timed是標(biāo)志超時(shí)銷毀 核心線程池也是可以銷毀的
            boolean timed = allowCoreThreadTimeOut || wc > corePoolSize;
            if ((wc > maximumPoolSize || (timed && timedOut))
                && (wc > 1 || workQueue.isEmpty())) {
                if (compareAndDecrementWorkerCount(c))
                    return null;
                continue;
            }
            try {
                Runnable r = timed ?
                    workQueue.poll(keepAliveTime, TimeUnit.NANOSECONDS) :
                    workQueue.take();
                if (r != null)
                    return r;
                timedOut = true;
            } catch (InterruptedException retry) {
                timedOut = false;
            }
        }
    }

    private void processWorkerExit(Worker w, boolean completedAbruptly) {
        if (completedAbruptly) // If abrupt, then workerCount wasn't adjusted
            decrementWorkerCount();
        final ReentrantLock mainLock = this.mainLock;
        mainLock.lock();
        try {
            completedTaskCount += w.completedTasks;
            workers.remove(w);
        } finally {
            mainLock.unlock();
        }
        tryTerminate();
        int c = ctl.get();
        if (runStateLessThan(c, STOP)) {
            if (!completedAbruptly) {
                int min = allowCoreThreadTimeOut ? 0 : corePoolSize;
                if (min == 0 && ! workQueue.isEmpty())
                    min = 1;
                if (workerCountOf(c) >= min)
                    return; // replacement not needed
            }
            addWorker(null, false);
        }
    }

   private void delayedExecute(RunnableScheduledFuture<?> task) {
   		//如果線程池不是RUNNING狀態(tài)，則使用拒絕策略把提交任務(wù)拒絕掉
        if (isShutdown())
            reject(task);
        else {
        //與ThreadPoolExecutor不同，這里直接把任務(wù)加入延遲隊(duì)列
            super.getQueue().add(task);
            //如果當(dāng)前狀態(tài)無(wú)法執(zhí)行任務(wù)，則取消
            if (isShutdown() &&
                !canRunInCurrentRunState(task.isPeriodic()) &&
                remove(task))
                task.cancel(false);
            else
            //和ThreadPoolExecutor不一樣，corePoolSize沒(méi)有達(dá)到會(huì)增加Worker;
            //增加Worker，確保提交的任務(wù)能夠被執(zhí)行
                ensurePrestart();
        }
    }

public boolean add(Runnable e) {
            return offer(e);
        }
public boolean offer(Runnable x) {
            if (x == null)
                throw new NullPointerException();
            RunnableScheduledFuture<?> e = (RunnableScheduledFuture<?>)x;
            final ReentrantLock lock = this.lock;
            lock.lock();
            try {
                int i = size;
                if (i >= queue.length)
                //容量擴(kuò)增50%
                    grow();
                size = i + 1;
                if (i == 0) {
                    queue[0] = e;
                    setIndex(e, 0);
                } else {
                //插入堆尾
                    siftUp(i, e);
                }
                if (queue[0] == e) {
                //如果新加入的元素成為了堆頂,則原先的leader就無(wú)效了
                    leader = null;
               //由于原先leader已經(jīng)無(wú)效被設(shè)置為null了,這里隨便喚醒一個(gè)線程(未必是原先的leader)來(lái)取走堆頂任務(wù)
                    available.signal();
                }
            } finally {
                lock.unlock();
            }
            return true;
        }

 private void siftUp(int k, RunnableScheduledFuture<?> key) {
            while (k > 0) {
            //獲取父節(jié)點(diǎn)
                int parent = (k - 1) >>> 1;
                RunnableScheduledFuture<?> e = queue[parent];
                //如果key節(jié)點(diǎn)的執(zhí)行時(shí)間大于父節(jié)點(diǎn)的執(zhí)行時(shí)間，不需要再排序了
                if (key.compareTo(e) >= 0)
                    break;
                    //如果key.compareTo(e)<0，說(shuō)明key節(jié)點(diǎn)的執(zhí)行時(shí)間小于父節(jié)點(diǎn)的執(zhí)行時(shí)間，需要把父節(jié)點(diǎn)移到后面
                queue[k] = e;
                setIndex(e, k);
                //設(shè)置索引為k
                k = parent;
            }
            //key設(shè)置為排序后的位置中
            queue[k] = key;
            setIndex(key, k);
        }

public void run() {
			//是否周期性，就是判斷period是否為0
            boolean periodic = isPeriodic();
            //檢查任務(wù)是否可以被執(zhí)行
            if (!canRunInCurrentRunState(periodic))
                cancel(false);
            //如果非周期性任務(wù)直接調(diào)用run運(yùn)行即可
            else if (!periodic)
                ScheduledFutureTask.super.run();
            //如果成功runAndRest，則設(shè)置下次運(yùn)行時(shí)間并調(diào)用reExecutePeriodic
            else if (ScheduledFutureTask.super.runAndReset()) {
                setNextRunTime();
            //需要重新將任務(wù)(outerTask)放到工作隊(duì)列中。此方法源碼會(huì)在后文介紹ScheduledThreadPoolExecutor本身API時(shí)提及
                reExecutePeriodic(outerTask);
            }
        }

		private void setNextRunTime() {
            long p = period;
            //fixed‐rate模式，時(shí)間設(shè)置為上一次時(shí)間+p,這里的時(shí)間只是可以被執(zhí)行的最小時(shí)間，不代表到點(diǎn)就要執(zhí)行
            if (p > 0)
                time += p;
            else
            //fixed‐delay模式，計(jì)算下一次任務(wù)可以被執(zhí)行的時(shí)間, 差不多就是當(dāng)前時(shí)間+delay值
                time = triggerTime(-p);
        }
        long triggerTime(long delay) {
        //如果delay<Long.Max_VALUE/2,則下次執(zhí)行時(shí)間為當(dāng)前時(shí)間+delay,否則為了避免隊(duì)列中出現(xiàn)由于溢出導(dǎo)致的排序紊亂,需要調(diào)用overflowFree來(lái)修正一下delay
        return now() +
            ((delay < (Long.MAX_VALUE >> 1)) ? delay : overflowFree(delay));
    }
    /**
    * 主要就是有這么一種情況：
    * 工作隊(duì)列中維護(hù)任務(wù)順序是基于compareTo的，在compareTo中比較兩個(gè)任務(wù)的順序會(huì)用time相減，負(fù)數(shù)則說(shuō)明優(yōu)先級(jí)高,那么就有可能出現(xiàn)一個(gè)delay為正數(shù),減去另一個(gè)為負(fù)數(shù)的delay，結(jié)果上溢為負(fù)數(shù)，則會(huì)導(dǎo)致compareTo產(chǎn)生錯(cuò)誤的結(jié)果.
    * 為了特殊處理這種情況，首先判斷一下隊(duì)首的delay是不是負(fù)數(shù)，如果是正數(shù)不用管了,怎么減都不會(huì)溢出。
    * 否則可以拿當(dāng)前delay減去隊(duì)首的delay來(lái)比較看，如果不出現(xiàn)上溢，則整個(gè)隊(duì)列都o(jì)k，排序不會(huì)亂。
    * 不然就把當(dāng)前delay值給調(diào)整為L(zhǎng)ong.MAX_VALUE+隊(duì)首delay
    /
   private long overflowFree(long delay) {
        Delayed head = (Delayed) super.getQueue().peek();
        if (head != null) {
            long headDelay = head.getDelay(NANOSECONDS);
            if (headDelay < 0 && (delay - headDelay < 0))
                delay = Long.MAX_VALUE + headDelay;
        }
        return delay;
    }