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

Creates a new {@code ThreadPoolExecutor} with the given initial parameters and default thread factory and rejected execution handler. It may be more convenient to use one of the Executors factory methods instead of this general purpose constructor.

Parameters:

corePoolSize - the number of threads to keep in the pool, even if they are idle, unless {@code allowCoreThreadTimeOut} is set

maximumPoolSize - the maximum number of threads to allow in the pool

keepAliveTime - when the number of threads is greater than the core, this is the maximum time that excess idle threads will wait for new tasks before terminating.

unit - the time unit for the {@code keepAliveTime} argument

workQueue - the queue to use for holding tasks before they are executed. This queue will hold only the {@code Runnable} tasks submitted by the {@code execute} method.

Throws:

IllegalArgumentException - if one of the following holds:
{@code corePoolSize < 0}
{@code keepAliveTime < 0}
{@code maximumPoolSize <= 0}
{@code maximumPoolSize < corePoolSize}

NullPointerException - if {@code workQueue} is null

 public ThreadPoolExecutor(int corePoolSize,
    int maximumPoolSize,
    long keepAliveTime,
    TimeUnit unit,
    BlockingQueue<Runnable> workQueue,
    ThreadFactory threadFactory) 
{
        this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
             threadFactory, defaultHandler);
}

Creates a new {@code ThreadPoolExecutor} with the given initial parameters and default rejected execution handler.

Parameters:

corePoolSize - the number of threads to keep in the pool, even if they are idle, unless {@code allowCoreThreadTimeOut} is set

maximumPoolSize - the maximum number of threads to allow in the pool

keepAliveTime - when the number of threads is greater than the core, this is the maximum time that excess idle threads will wait for new tasks before terminating.

unit - the time unit for the {@code keepAliveTime} argument

workQueue - the queue to use for holding tasks before they are executed. This queue will hold only the {@code Runnable} tasks submitted by the {@code execute} method.

threadFactory - the factory to use when the executor creates a new thread

Throws:

IllegalArgumentException - if one of the following holds:
{@code corePoolSize < 0}
{@code keepAliveTime < 0}
{@code maximumPoolSize <= 0}
{@code maximumPoolSize < corePoolSize}

NullPointerException - if {@code workQueue} or {@code threadFactory} is null

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

Creates a new {@code ThreadPoolExecutor} with the given initial parameters and default thread factory.

Parameters:

corePoolSize - the number of threads to keep in the pool, even if they are idle, unless {@code allowCoreThreadTimeOut} is set

maximumPoolSize - the maximum number of threads to allow in the pool

keepAliveTime - when the number of threads is greater than the core, this is the maximum time that excess idle threads will wait for new tasks before terminating.

unit - the time unit for the {@code keepAliveTime} argument

workQueue - the queue to use for holding tasks before they are executed. This queue will hold only the {@code Runnable} tasks submitted by the {@code execute} method.

handler - the handler to use when execution is blocked because the thread bounds and queue capacities are reached

Throws:

IllegalArgumentException - if one of the following holds:
{@code corePoolSize < 0}
{@code keepAliveTime < 0}
{@code maximumPoolSize <= 0}
{@code maximumPoolSize < corePoolSize}

NullPointerException - if {@code workQueue} or {@code handler} is null

 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;
}

Creates a new {@code ThreadPoolExecutor} with the given initial parameters.

Parameters:

corePoolSize - the number of threads to keep in the pool, even if they are idle, unless {@code allowCoreThreadTimeOut} is set

maximumPoolSize - the maximum number of threads to allow in the pool

keepAliveTime - when the number of threads is greater than the core, this is the maximum time that excess idle threads will wait for new tasks before terminating.

unit - the time unit for the {@code keepAliveTime} argument

workQueue - the queue to use for holding tasks before they are executed. This queue will hold only the {@code Runnable} tasks submitted by the {@code execute} method.

threadFactory - the factory to use when the executor creates a new thread

handler - the handler to use when execution is blocked because the thread bounds and queue capacities are reached

Throws:

IllegalArgumentException - if one of the following holds:
{@code corePoolSize < 0}
{@code keepAliveTime < 0}
{@code maximumPoolSize <= 0}
{@code maximumPoolSize < corePoolSize}

NullPointerException - if {@code workQueue} or {@code threadFactory} or {@code handler} is null

 protected  void afterExecute(Runnable r,
    Throwable t) 
{

}

Method invoked upon completion of execution of the given Runnable. This method is invoked by the thread that executed the task. If non-null, the Throwable is the uncaught {@code RuntimeException} or {@code Error} that caused execution to terminate abruptly.

This implementation does nothing, but may be customized in subclasses. Note: To properly nest multiple overridings, subclasses should generally invoke {@code super.afterExecute} at the beginning of this method.

Note: When actions are enclosed in tasks (such as FutureTask ) either explicitly or via methods such as {@code submit}, these task objects catch and maintain computational exceptions, and so they do not cause abrupt termination, and the internal exceptions are not passed to this method. If you would like to trap both kinds of failures in this method, you can further probe for such cases, as in this sample subclass that prints either the direct cause or the underlying exception if a task has been aborted:

 {@code
class ExtendedExecutor extends ThreadPoolExecutor {
  // ...
  protected void afterExecute(Runnable r, Throwable t) {
    super.afterExecute(r, t);
    if (t == null && r instanceof Future) {
      try {
        Object result = ((Future) r).get();
      } catch (CancellationException ce) {
          t = ce;
      } catch (ExecutionException ee) {
          t = ee.getCause();
      } catch (InterruptedException ie) {
          Thread.currentThread().interrupt(); // ignore/reset
      }
    }
    if (t != null)
      System.out.println(t);
  }
}}

 public  void allowCoreThreadTimeOut(boolean value) 
{
        if (value && keepAliveTime < = 0)
            throw new IllegalArgumentException("Core threads must have nonzero keep alive times");
        if (value != allowCoreThreadTimeOut) {
            allowCoreThreadTimeOut = value;
            if (value)
                interruptIdleWorkers();
        }
}

Sets the policy governing whether core threads may time out and terminate if no tasks arrive within the keep-alive time, being replaced if needed when new tasks arrive. When false, core threads are never terminated due to lack of incoming tasks. When true, the same keep-alive policy applying to non-core threads applies also to core threads. To avoid continual thread replacement, the keep-alive time must be greater than zero when setting {@code true}. This method should in general be called before the pool is actively used.

 public boolean allowsCoreThreadTimeOut() 
{
        return allowCoreThreadTimeOut;
}

Returns true if this pool allows core threads to time out and terminate if no tasks arrive within the keepAlive time, being replaced if needed when new tasks arrive. When true, the same keep-alive policy applying to non-core threads applies also to core threads. When false (the default), core threads are never terminated due to lack of incoming tasks.

 public boolean awaitTermination(long timeout,
    TimeUnit unit) throws InterruptedException 
{
        long nanos = unit.toNanos(timeout);
        final ReentrantLock mainLock = this.mainLock;
        mainLock.lock();
        try {
            for (;;) {
                if (runStateAtLeast(ctl.get(), TERMINATED))
                    return true;
                if (nanos < = 0)
                    return false;
                nanos = termination.awaitNanos(nanos);
            }
        } finally {
            mainLock.unlock();
        }
}

 protected  void beforeExecute(Thread t,
    Runnable r) 
{

}

Method invoked prior to executing the given Runnable in the given thread. This method is invoked by thread {@code t} that will execute task {@code r}, and may be used to re-initialize ThreadLocals, or to perform logging.

This implementation does nothing, but may be customized in subclasses. Note: To properly nest multiple overridings, subclasses should generally invoke {@code super.beforeExecute} at the end of this method.

 public  void execute(Runnable command) 
{
        if (command == null)
            throw new NullPointerException();
        /*
         * Proceed in 3 steps:
         *
         * 1. If fewer than corePoolSize threads are running, try to
         * start a new thread with the given command as its first
         * task.  The call to addWorker atomically checks runState and
         * workerCount, and so prevents false alarms that would add
         * threads when it shouldn't, by returning false.
         *
         * 2. If a task can be successfully queued, then we still need
         * to double-check whether we should have added a thread
         * (because existing ones died since last checking) or that
         * the pool shut down since entry into this method. So we
         * recheck state and if necessary roll back the enqueuing if
         * stopped, or start a new thread if there are none.
         *
         * 3. If we cannot queue task, then we try to add a new
         * thread.  If it fails, we know we are shut down or saturated
         * and so reject the task.
         */
        int c = ctl.get();
        if (workerCountOf(c) <  corePoolSize) {
            if (addWorker(command, true))
                return;
            c = ctl.get();
        }
        if (isRunning(c) && workQueue.offer(command)) {
            int recheck = ctl.get();
            if (! isRunning(recheck) && remove(command))
                reject(command);
            else if (workerCountOf(recheck) == 0)
                addWorker(null, false);
        }
        else if (!addWorker(command, false))
            reject(command);
}

Executes the given task sometime in the future. The task may execute in a new thread or in an existing pooled thread. If the task cannot be submitted for execution, either because this executor has been shutdown or because its capacity has been reached, the task is handled by the current {@code RejectedExecutionHandler}.

 protected  void finalize() 
{
        shutdown();
}

Invokes {@code shutdown} when this executor is no longer referenced and it has no threads.

 public int getActiveCount() 
{
        final ReentrantLock mainLock = this.mainLock;
        mainLock.lock();
        try {
            int n = 0;
            for (Worker w : workers)
                if (w.isLocked())
                    ++n;
            return n;
        } finally {
            mainLock.unlock();
        }
}

Returns the approximate number of threads that are actively executing tasks.

 public long getCompletedTaskCount() 
{
        final ReentrantLock mainLock = this.mainLock;
        mainLock.lock();
        try {
            long n = completedTaskCount;
            for (Worker w : workers)
                n += w.completedTasks;
            return n;
        } finally {
            mainLock.unlock();
        }
}

Returns the approximate total number of tasks that have completed execution. Because the states of tasks and threads may change dynamically during computation, the returned value is only an approximation, but one that does not ever decrease across successive calls.

 public int getCorePoolSize() 
{
        return corePoolSize;
}

Returns the core number of threads.

 public long getKeepAliveTime(TimeUnit unit) 
{
        return unit.convert(keepAliveTime, TimeUnit.NANOSECONDS);
}

Returns the thread keep-alive time, which is the amount of time that threads in excess of the core pool size may remain idle before being terminated.

 public int getLargestPoolSize() 
{
        final ReentrantLock mainLock = this.mainLock;
        mainLock.lock();
        try {
            return largestPoolSize;
        } finally {
            mainLock.unlock();
        }
}

Returns the largest number of threads that have ever simultaneously been in the pool.

 public int getMaximumPoolSize() 
{
        return maximumPoolSize;
}

Returns the maximum allowed number of threads.

 public int getPoolSize() 
{
        final ReentrantLock mainLock = this.mainLock;
        mainLock.lock();
        try {
            // Remove rare and surprising possibility of
            // isTerminated() && getPoolSize()  > 0
            return runStateAtLeast(ctl.get(), TIDYING) ? 0
                : workers.size();
        } finally {
            mainLock.unlock();
        }
}

Returns the current number of threads in the pool.

 public BlockingQueue<Runnable> getQueue() 
{
        return workQueue;
}

Returns the task queue used by this executor. Access to the task queue is intended primarily for debugging and monitoring. This queue may be in active use. Retrieving the task queue does not prevent queued tasks from executing.

 public RejectedExecutionHandler getRejectedExecutionHandler() 
{
        return handler;
}

Returns the current handler for unexecutable tasks.

 public long getTaskCount() 
{
        final ReentrantLock mainLock = this.mainLock;
        mainLock.lock();
        try {
            long n = completedTaskCount;
            for (Worker w : workers) {
                n += w.completedTasks;
                if (w.isLocked())
                    ++n;
            }
            return n + workQueue.size();
        } finally {
            mainLock.unlock();
        }
}

Returns the approximate total number of tasks that have ever been scheduled for execution. Because the states of tasks and threads may change dynamically during computation, the returned value is only an approximation.

 public ThreadFactory getThreadFactory() 
{
        return threadFactory;
}

Returns the thread factory used to create new threads.

 final boolean isRunningOrShutdown(boolean shutdownOK) 
{
        int rs = runStateOf(ctl.get());
        return rs == RUNNING || (rs == SHUTDOWN && shutdownOK);
}

State check needed by ScheduledThreadPoolExecutor to enable running tasks during shutdown.

 public boolean isShutdown() 
{
        return ! isRunning(ctl.get());
}

 public boolean isTerminated() 
{
        return runStateAtLeast(ctl.get(), TERMINATED);
}

 public boolean isTerminating() 
{
        int c = ctl.get();
        return ! isRunning(c) && runStateLessThan(c, TERMINATED);
}

Returns true if this executor is in the process of terminating after #shutdown or #shutdownNow but has not completely terminated. This method may be useful for debugging. A return of {@code true} reported a sufficient period after shutdown may indicate that submitted tasks have ignored or suppressed interruption, causing this executor not to properly terminate.

  void onShutdown() 
{

}

Performs any further cleanup following run state transition on invocation of shutdown. A no-op here, but used by ScheduledThreadPoolExecutor to cancel delayed tasks.

 public int prestartAllCoreThreads() 
{
        int n = 0;
        while (addWorker(null, true))
            ++n;
        return n;
}

Starts all core threads, causing them to idly wait for work. This overrides the default policy of starting core threads only when new tasks are executed.

 public boolean prestartCoreThread() 
{
        return workerCountOf(ctl.get()) <  corePoolSize &&
            addWorker(null, true);
}

Starts a core thread, causing it to idly wait for work. This overrides the default policy of starting core threads only when new tasks are executed. This method will return {@code false} if all core threads have already been started.

 public  void purge() 
{
        final BlockingQueue< Runnable > q = workQueue;
        try {
            Iterator< Runnable > it = q.iterator();
            while (it.hasNext()) {
                Runnable r = it.next();
                if (r instanceof Future< ? > && ((Future< ? >)r).isCancelled())
                    it.remove();
            }
        } catch (ConcurrentModificationException fallThrough) {
            // Take slow path if we encounter interference during traversal.
            // Make copy for traversal and call remove for cancelled entries.
            // The slow path is more likely to be O(N*N).
            for (Object r : q.toArray())
                if (r instanceof Future< ? > && ((Future< ? >)r).isCancelled())
                    q.remove(r);
        }
        tryTerminate(); // In case SHUTDOWN and now empty
}

Tries to remove from the work queue all Future tasks that have been cancelled. This method can be useful as a storage reclamation operation, that has no other impact on functionality. Cancelled tasks are never executed, but may accumulate in work queues until worker threads can actively remove them. Invoking this method instead tries to remove them now. However, this method may fail to remove tasks in the presence of interference by other threads.

 final  void reject(Runnable command) 
{
        handler.rejectedExecution(command, this);
}

Invokes the rejected execution handler for the given command. Package-protected for use by ScheduledThreadPoolExecutor.

 public boolean remove(Runnable task) 
{
        boolean removed = workQueue.remove(task);
        tryTerminate(); // In case SHUTDOWN and now empty
        return removed;
}

Removes this task from the executor's internal queue if it is present, thus causing it not to be run if it has not already started.

This method may be useful as one part of a cancellation scheme. It may fail to remove tasks that have been converted into other forms before being placed on the internal queue. For example, a task entered using {@code submit} might be converted into a form that maintains {@code Future} status. However, in such cases, method #purge may be used to remove those Futures that have been cancelled.

 final  void runWorker(Worker w) 
{
        Runnable task = w.firstTask;
        w.firstTask = null;
        boolean completedAbruptly = true;
        try {
            while (task != null || (task = getTask()) != null) {
                w.lock();
                clearInterruptsForTaskRun();
                try {
                    beforeExecute(w.thread, 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);
        }
}

Main worker run loop. Repeatedly gets tasks from queue and executes them, while coping with a number of issues: 1. We may start out with an initial task, in which case we don't need to get the first one. Otherwise, as long as pool is running, we get tasks from getTask. If it returns null then the worker exits due to changed pool state or configuration parameters. Other exits result from exception throws in external code, in which case completedAbruptly holds, which usually leads processWorkerExit to replace this thread. 2. Before running any task, the lock is acquired to prevent other pool interrupts while the task is executing, and clearInterruptsForTaskRun called to ensure that unless pool is stopping, this thread does not have its interrupt set. 3. Each task run is preceded by a call to beforeExecute, which might throw an exception, in which case we cause thread to die (breaking loop with completedAbruptly true) without processing the task. 4. Assuming beforeExecute completes normally, we run the task, gathering any of its thrown exceptions to send to afterExecute. We separately handle RuntimeException, Error (both of which the specs guarantee that we trap) and arbitrary Throwables. Because we cannot rethrow Throwables within Runnable.run, we wrap them within Errors on the way out (to the thread's UncaughtExceptionHandler). Any thrown exception also conservatively causes thread to die. 5. After task.run completes, we call afterExecute, which may also throw an exception, which will also cause thread to die. According to JLS Sec 14.20, this exception is the one that will be in effect even if task.run throws. The net effect of the exception mechanics is that afterExecute and the thread's UncaughtExceptionHandler have as accurate information as we can provide about any problems encountered by user code.

 public  void setCorePoolSize(int corePoolSize) 
{
        if (corePoolSize <  0)
            throw new IllegalArgumentException();
        int delta = corePoolSize - this.corePoolSize;
        this.corePoolSize = corePoolSize;
        if (workerCountOf(ctl.get())  > corePoolSize)
            interruptIdleWorkers();
        else if (delta  > 0) {
            // We don't really know how many new threads are "needed".
            // As a heuristic, prestart enough new workers (up to new
            // core size) to handle the current number of tasks in
            // queue, but stop if queue becomes empty while doing so.
            int k = Math.min(delta, workQueue.size());
            while (k--  > 0 && addWorker(null, true)) {
                if (workQueue.isEmpty())
                    break;
            }
        }
}

Sets the core number of threads. This overrides any value set in the constructor. If the new value is smaller than the current value, excess existing threads will be terminated when they next become idle. If larger, new threads will, if needed, be started to execute any queued tasks.

 public  void setKeepAliveTime(long time,
    TimeUnit unit) 
{
        if (time <  0)
            throw new IllegalArgumentException();
        if (time == 0 && allowsCoreThreadTimeOut())
            throw new IllegalArgumentException("Core threads must have nonzero keep alive times");
        long keepAliveTime = unit.toNanos(time);
        long delta = keepAliveTime - this.keepAliveTime;
        this.keepAliveTime = keepAliveTime;
        if (delta <  0)
            interruptIdleWorkers();
}

Sets the time limit for which threads may remain idle before being terminated. If there are more than the core number of threads currently in the pool, after waiting this amount of time without processing a task, excess threads will be terminated. This overrides any value set in the constructor.

 public  void setMaximumPoolSize(int maximumPoolSize) 
{
        if (maximumPoolSize < = 0 || maximumPoolSize <  corePoolSize)
            throw new IllegalArgumentException();
        this.maximumPoolSize = maximumPoolSize;
        if (workerCountOf(ctl.get())  > maximumPoolSize)
            interruptIdleWorkers();
}

Sets the maximum allowed number of threads. This overrides any value set in the constructor. If the new value is smaller than the current value, excess existing threads will be terminated when they next become idle.

 public  void setRejectedExecutionHandler(RejectedExecutionHandler handler) 
{
        if (handler == null)
            throw new NullPointerException();
        this.handler = handler;
}

Sets a new handler for unexecutable tasks.

 public  void setThreadFactory(ThreadFactory threadFactory) 
{
        if (threadFactory == null)
            throw new NullPointerException();
        this.threadFactory = threadFactory;
}

Sets the thread factory used to create new threads.

 public  void shutdown() 
{
        final ReentrantLock mainLock = this.mainLock;
        mainLock.lock();
        try {
            checkShutdownAccess();
            advanceRunState(SHUTDOWN);
            interruptIdleWorkers();
            onShutdown(); // hook for ScheduledThreadPoolExecutor
        } finally {
            mainLock.unlock();
        }
        tryTerminate();
}

Initiates an orderly shutdown in which previously submitted tasks are executed, but no new tasks will be accepted. Invocation has no additional effect if already shut down.

This method does not wait for previously submitted tasks to complete execution. Use awaitTermination to do that.

 public List<Runnable> shutdownNow() 
{
        List< Runnable > tasks;
        final ReentrantLock mainLock = this.mainLock;
        mainLock.lock();
        try {
            checkShutdownAccess();
            advanceRunState(STOP);
            interruptWorkers();
            tasks = drainQueue();
        } finally {
            mainLock.unlock();
        }
        tryTerminate();
        return tasks;
}

Attempts to stop all actively executing tasks, halts the processing of waiting tasks, and returns a list of the tasks that were awaiting execution. These tasks are drained (removed) from the task queue upon return from this method.

This method does not wait for actively executing tasks to terminate. Use awaitTermination to do that.

There are no guarantees beyond best-effort attempts to stop processing actively executing tasks. This implementation cancels tasks via Thread#interrupt , so any task that fails to respond to interrupts may never terminate.

 protected  void terminated() 
{

}

Method invoked when the Executor has terminated. Default implementation does nothing. Note: To properly nest multiple overridings, subclasses should generally invoke {@code super.terminated} within this method.

 public String toString() 
{
        long ncompleted;
        int nworkers, nactive;
        final ReentrantLock mainLock = this.mainLock;
        mainLock.lock();
        try {
            ncompleted = completedTaskCount;
            nactive = 0;
            nworkers = workers.size();
            for (Worker w : workers) {
                ncompleted += w.completedTasks;
                if (w.isLocked())
                    ++nactive;
            }
        } finally {
            mainLock.unlock();
        }
        int c = ctl.get();
        String rs = (runStateLessThan(c, SHUTDOWN) ? "Running" :
                     (runStateAtLeast(c, TERMINATED) ? "Terminated" :
                      "Shutting down"));
        return super.toString() +
            "[" + rs +
            ", pool size = " + nworkers +
            ", active threads = " + nactive +
            ", queued tasks = " + workQueue.size() +
            ", completed tasks = " + ncompleted +
            "]";
}

Returns a string identifying this pool, as well as its state, including indications of run state and estimated worker and task counts.

 final  void tryTerminate() 
{
        for (;;) {
            int c = ctl.get();
            if (isRunning(c) ||
                runStateAtLeast(c, TIDYING) ||
                (runStateOf(c) == SHUTDOWN && ! workQueue.isEmpty()))
                return;
            if (workerCountOf(c) != 0) { // Eligible to terminate
                interruptIdleWorkers(ONLY_ONE);
                return;
            }
            final ReentrantLock mainLock = this.mainLock;
            mainLock.lock();
            try {
                if (ctl.compareAndSet(c, ctlOf(TIDYING, 0))) {
                    try {
                        terminated();
                    } finally {
                        ctl.set(ctlOf(TERMINATED, 0));
                        termination.signalAll();
                    }
                    return;
                }
            } finally {
                mainLock.unlock();
            }
            // else retry on failed CAS
        }
}

Transitions to TERMINATED state if either (SHUTDOWN and pool and queue empty) or (STOP and pool empty). If otherwise eligible to terminate but workerCount is nonzero, interrupts an idle worker to ensure that shutdown signals propagate. This method must be called following any action that might make termination possible -- reducing worker count or removing tasks from the queue during shutdown. The method is non-private to allow access from ScheduledThreadPoolExecutor.