Analisis kod sumber prinsip pelaksanaan kolam benang Java

    // 复合类型变量 是一个原子整数  控制状态（运行状态|线程池活跃线程数量）
    private final AtomicInteger ctl = new AtomicInteger(ctlOf(RUNNING, 0)); 
    private static final int COUNT_BITS = Integer.SIZE - 3; // 低29位 
    private static final int CAPACITY   = (1 << COUNT_BITS) - 1; // 容量
    // 运行状态存储在高位3位
    private static final int RUNNING    = -1 << COUNT_BITS;  // 接受新任务，并处理队列任务
    private static final int SHUTDOWN   =  0 << COUNT_BITS;  // 不接受新任务，但会处理队列任务
    private static final int STOP       =  1 << COUNT_BITS;  // 不接受新任务，不会处理队列任务，中断正在处理的任务
    private static final int TIDYING    =  2 << COUNT_BITS;  // 所有的任务已结束，活跃线程为0，线程过渡到TIDYING状       态，将会执行terminated()钩子方法
    private static final int TERMINATED =  3 << COUNT_BITS;  // terminated()方法已经完成
    // 设置 ctl 参数方法
    private static int runStateOf(int c)     { return c & ~CAPACITY; }
    private static int workerCountOf(int c)  { return c & CAPACITY; }
    private static int ctlOf(int rs, int wc) { return rs | wc; }
    /**
     * 阻塞队列
     */
    private final BlockingQueue<Runnable> workQueue;
    /**
     * Lock 锁.
     */
    private final ReentrantLock mainLock = new ReentrantLock();
    /**
     * 工人们
     */
    private final HashSet<Worker> workers = new HashSet<Worker>();
    /**
     * 等待条件支持等待终止
     */
    private final Condition termination = mainLock.newCondition();
    /**
     * 最大的池大小.
     */
    private int largestPoolSize;
    /**
     * 完成任务数
     */
    private long completedTaskCount;
    /**
     * 线程工厂
     */
    private volatile ThreadFactory threadFactory;
    /**
     * 拒绝策略
     */
    private volatile RejectedExecutionHandler handler;
    /**
     * 存活时间
     */
    private volatile long keepAliveTime;
    /**
     * 允许核心线程数
     */
    private volatile boolean allowCoreThreadTimeOut;
    /**
     * 核心线程数
     */
    private volatile int corePoolSize;
    /**
     * 最大线程数
     */
    private volatile int maximumPoolSize;
    /**
     * 默认拒绝策略
     */
    private static final RejectedExecutionHandler defaultHandler =
        new AbortPolicy();
    /**
     * shutdown and shutdownNow权限
     */
    private static final RuntimePermission shutdownPerm =
        new RuntimePermission("modifyThread");

    public ThreadPoolExecutor(int corePoolSize,
                              int maximumPoolSize,
                              long keepAliveTime,
                              TimeUnit unit,
                              BlockingQueue<Runnable> workQueue) {
        this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
             Executors.defaultThreadFactory(), defaultHandler);
    }
    public ThreadPoolExecutor(int corePoolSize,
                              int maximumPoolSize,
                              long keepAliveTime,
                              TimeUnit unit,
                              BlockingQueue<Runnable> workQueue,
                              ThreadFactory threadFactory) {
        this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
             threadFactory, defaultHandler);
    }
    public ThreadPoolExecutor(int corePoolSize,
                              int maximumPoolSize,
                              long keepAliveTime,
                              TimeUnit unit,
                              BlockingQueue<Runnable> workQueue,
                              RejectedExecutionHandler handler) {
        this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
             Executors.defaultThreadFactory(), handler);
    }
    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.corePoolSize = corePoolSize;
        this.maximumPoolSize = maximumPoolSize;
        this.workQueue = workQueue;
        this.keepAliveTime = unit.toNanos(keepAliveTime);
        this.threadFactory = threadFactory;
        this.handler = handler;
    }

    private final class Worker
        extends AbstractQueuedSynchronizer
        implements Runnable
    {
        private static final long serialVersionUID = 6138294804551838833L;
        // 工人的本质就是个线程
        final Thread thread;
        // 第一件工作任务
        Runnable firstTask;
      volatile long completedTasks;
        /**
         * 构造器
         */
        Worker(Runnable firstTask) {
            setState(-1); // inhibit interrupts until runWorker
            this.firstTask = firstTask;
            this.thread = getThreadFactory().newThread(this);
        }
        /** 工作  */
        public void run() {
            runWorker(this);
        }
        protected boolean isHeldExclusively() {
            return getState() != 0;
        }
        protected boolean tryAcquire(int unused) {
            if (compareAndSetState(0, 1)) {
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }
            return false;
        }
        protected boolean tryRelease(int unused) {
            setExclusiveOwnerThread(null);
            setState(0);
            return true;
        }
        public void lock()        { acquire(1); }
        public boolean tryLock()  { return tryAcquire(1); }
        public void unlock()      { release(1); }
        public boolean isLocked() { return isHeldExclusively(); }
        void interruptIfStarted() {
            Thread t;
            if (getState() >= 0 && (t = thread) != null && !t.isInterrupted()) {
                try {
                    t.interrupt();
                } catch (SecurityException ignore) {
                }
            }
        }
    }

public abstract class AbstractExecutorService implements ExecutorService {
    public Future<?> submit(Runnable task) {
        if (task == null) throw new NullPointerException();
        RunnableFuture<Void> ftask = newTaskFor(task, null);
        execute(ftask);
        return ftask;
    }
    public <T> Future<T> submit(Runnable task, T result) {
        if (task == null) throw new NullPointerException();
        RunnableFuture<T> ftask = newTaskFor(task, result);
        execute(ftask);
        return ftask;
    }
    public <T> Future<T> submit(Callable<T> task) {
        if (task == null) throw new NullPointerException();
        RunnableFuture<T> ftask = newTaskFor(task);
        execute(ftask);
        return ftask;
    }
    ...
}

    private boolean addWorker(Runnable firstTask, boolean core) {
        retry:
        for (;;) {
            int c = ctl.get();
            int rs = runStateOf(c);
            // 判断状态，及任务列表
            if (rs >= SHUTDOWN &&
                ! (rs == SHUTDOWN &&
                   firstTask == null &&
                   ! workQueue.isEmpty()))
                return false;
            for (;;) {
                int wc = workerCountOf(c);
                if (wc >= CAPACITY ||
                    wc >= (core ? corePoolSize : maximumPoolSize))
                    return false;
                if (compareAndIncrementWorkerCount(c))
                    break retry;
                c = ctl.get();  // Re-read ctl
                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 {
            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());
                    if (rs < SHUTDOWN ||
                        (rs == SHUTDOWN && firstTask == null)) {
                        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) {
                    t.start();
                    workerStarted = true;
                }
            }
        } finally {
            if (! workerStarted)
                addWorkerFailed(w);
        }
        return workerStarted;
    }

    private Runnable getTask() {
        boolean timedOut = false; // Did the last poll() time out?
        for (;;) {
            int c = ctl.get();
            int rs = runStateOf(c);
            // Check if queue empty only if necessary.
            if (rs >= SHUTDOWN && (rs >= STOP || workQueue.isEmpty())) {
                decrementWorkerCount();
                return null;
            }
            int wc = workerCountOf(c);
            // Are workers subject to culling?
            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;
            }
        }
    }

   final void runWorker(Worker w) {
        Thread wt = Thread.currentThread();
        Runnable task = w.firstTask;
        w.firstTask = null;
        w.unlock(); // allow interrupts
        boolean completedAbruptly = true;
        try {
            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
                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 {
                    task = null;
                    w.completedTasks++;
                    w.unlock();
                }
            }
            completedAbruptly = false;
        } finally {
            processWorkerExit(w, completedAbruptly);
        }
    }