// 設(shè)置線程池時指定核心線程數(shù)、最大線程數(shù)、線程存活時間及等待隊列。
// 線程創(chuàng)建工廠和拒絕策略使用默認的（AbortPolicy）
public ThreadPoolExecutor(int corePoolSize,
                          int maximumPoolSize,
                          long keepAliveTime,
                          TimeUnit unit,
                          BlockingQueue<Runnable> workQueue) {
    this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
         Executors.defaultThreadFactory(), defaultHandler);
}
// 設(shè)置線程池時指定核心線程數(shù)、最大線程數(shù)、線程存活時間、等待隊列及線程創(chuàng)建工廠 
// 拒絕策略使用默認的（AbortPolicy）
public ThreadPoolExecutor(int corePoolSize,
                          int maximumPoolSize,
                          long keepAliveTime,
                          TimeUnit unit,
                          BlockingQueue<Runnable> workQueue,
                          ThreadFactory threadFactory) {
    this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
         threadFactory, defaultHandler);
}
// 設(shè)置線程池時指定核心線程數(shù)、最大線程數(shù)、線程存活時間、等待隊列及拒絕策略
// 線程創(chuàng)建工廠使用默認的
public ThreadPoolExecutor(int corePoolSize,
                              int maximumPoolSize,
                              long keepAliveTime,
                              TimeUnit unit,
                              BlockingQueue<Runnable> workQueue,
                              RejectedExecutionHandler handler) {
        this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
             Executors.defaultThreadFactory(), handler);
   }
// 設(shè)置線程池時指定核心線程數(shù)、最大線程數(shù)、線程存活時間、等待隊列、線程創(chuàng)建工廠及拒絕策略
public ThreadPoolExecutor(int corePoolSize,
                              int maximumPoolSize,
                              long keepAliveTime,
                              TimeUnit unit,
                              BlockingQueue<Runnable> workQueue,
                              ThreadFactory threadFactory,
                              RejectedExecutionHandler handler) {
        if (corePoolSize < 0 ||
            maximumPoolSize <= 0 ||
            maximumPoolSize < corePoolSize ||
            keepAliveTime < 0)
            throw new IllegalArgumentException();
        if (workQueue == null || threadFactory == null || handler == null)
            throw new NullPointerException();
        this.acc = System.getSecurityManager() == null ?
                null :
                AccessController.getContext();
        this.corePoolSize = corePoolSize;
        this.maximumPoolSize = maximumPoolSize;
        this.workQueue = workQueue;
        this.keepAliveTime = unit.toNanos(keepAliveTime);
        this.threadFactory = threadFactory;
        this.handler = handler;
    }

 public void execute(Runnable command) {
        // 判斷提交的任務(wù)command是否為null，若是null，則拋出空指針異常；
        if (command == null)
            throw new NullPointerException();
        // 獲取線程池中當前線程數(shù)
        int c = ctl.get();
        // 如果線程池中當前線程數(shù)小于核心池大小，進入if語句塊
        if (workerCountOf(c) < corePoolSize) {
            // 如果以給定的命令啟動一個核心線程執(zhí)行任務(wù)成功，直接返回
            if (addWorker(command, true))
                return;
            c = ctl.get();
        }
        // 如果當前線程池處于RUNNING狀態(tài)，則將任務(wù)放入任務(wù)緩存隊列
        if (isRunning(c) && workQueue.offer(command)) {
            int recheck = ctl.get();
            // 如果線程池不處于運行狀態(tài)并且移除剛加入的任務(wù)成功則執(zhí)行拒絕策略
            if (! isRunning(recheck) && remove(command))
                reject(command);
            // 如果當前線程數(shù)為0，則在線程池里增加一個線程，保證隊列里的任務(wù)不會沒有線程執(zhí)行
            else if (workerCountOf(recheck) == 0)
                addWorker(null, false);
        } 
        // 嘗試啟動核心線程之外的線程，如果不滿足，則執(zhí)行對應(yīng)的拒絕策略
        else if (!addWorker(command, false))
            reject(command);
    }

private boolean addWorker(Runnable firstTask, boolean core) {
        retry:
        for (;;) {
            int c = ctl.get();
            int rs = runStateOf(c);
            // 如果線程池狀態(tài)大于SHUTDOWN或者線程池狀態(tài)等于SHUTDOWN，firstTask不等于null
            // 或者線程池狀態(tài)等于SHUTDOWN,任務(wù)隊列等于空時，直接返回false結(jié)束。
            if (rs >= SHUTDOWN &&
                ! (rs == SHUTDOWN &&
                   firstTask == null &&
                   ! workQueue.isEmpty()))
                return false;
            for (;;) {
                int wc = workerCountOf(c);
                // 如果線程數(shù)量大于等于最大數(shù)量或者大于等于上限
                //（入?yún)ore傳true,取核心線程數(shù)，否則取最大線程數(shù)），直接返回false結(jié)束。
                if (wc >= CAPACITY ||
                    wc >= (core ? corePoolSize : maximumPoolSize))
                    return false
                // CAS操作給工作線程數(shù)加1，成功則跳到retry處，不再進入循環(huán)。
                if (compareAndIncrementWorkerCount(c))
                    break retry;
                c = ctl.get();  // Re-read ctl
                // 如果線程池狀態(tài)與剛進入時不一致，則跳到retry處，再次進入循環(huán)
                if (runStateOf(c) != rs)
                    continue retry;
                // else CAS failed due to workerCount change; retry inner loop
            }
        }
        boolean workerStarted = false;
        boolean workerAdded = false;
        Worker w = null;
        try {
            // 新建一個線程
            w = new Worker(firstTask);
            final Thread t = w.thread;
            if (t != null) {
                final ReentrantLock mainLock = this.mainLock;
                mainLock.lock();
                try {
                    int rs = runStateOf(ctl.get());
                    // 如果線程池狀態(tài)在SHUTDOWN之前或者
                    // 線程池狀態(tài)等于SHUTDOWN并且firstTask等于null時，進入處理。
                    if (rs < SHUTDOWN ||
                        (rs == SHUTDOWN && firstTask == null)) {
                        // 如果要執(zhí)行的線程正在運行，則拋異常
                        if (t.isAlive()) // precheck that t is startable
                            throw new IllegalThreadStateException();
                        workers.add(w);
                        int s = workers.size();
                        if (s > largestPoolSize)
                            largestPoolSize = s;
                        workerAdded = true;
                    }
                } finally {
                    mainLock.unlock();
                }
                if (workerAdded) {
                    // 啟動線程
                    t.start();
                    workerStarted = true;
                }
            }
        } finally {
            // 如果線程添加失敗，則將新增的對應(yīng)信息刪除
            if (! workerStarted)
                addWorkerFailed(w);
        }
        return workerStarted;
    }

public void run() {
            runWorker(this);
        }
final void runWorker(Worker w) {
        Thread wt = Thread.currentThread();
        Runnable task = w.firstTask;
        w.firstTask = null;
        w.unlock(); // allow interrupts
        boolean completedAbruptly = true;
        try {
            // 如果任務(wù)不為空或者新獲取到的任務(wù)不為空
            while (task != null || (task = getTask()) != null) {
                w.lock();
                // 當線程池狀態(tài)，大于等于 STOP 時，保證工作線程都有中斷標志。
                // 當線程池狀態(tài)，小于STOP時，保證工作線程都沒有中斷標志。
                if ((runStateAtLeast(ctl.get(), STOP) ||
                     (Thread.interrupted() &&
                      runStateAtLeast(ctl.get(), STOP))) &&
                    !wt.isInterrupted())
                    wt.interrupt();
                try {
                    beforeExecute(wt, task);
                    Throwable thrown = null;
                    try {
                        // 執(zhí)行任務(wù)
                        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 {
                    task = null;
                    w.completedTasks++;
                    w.unlock();
                }
            }
            completedAbruptly = false;
        } finally {
            processWorkerExit(w, completedAbruptly);
        }
    }