ScheduledThreadPoolExecutor

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 RuntimeException or 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 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 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
          &amp;&amp; r instanceof Future&lt;?&gt;
          &amp;&amp; ((Future&lt;?&gt;)r).isDone()) {
        try {
          Object result = ((Future&lt;?&gt;) r).get();
        } catch (CancellationException ce) {
          t = ce;
        } catch (ExecutionException ee) {
          t = ee.getCause();
        } catch (InterruptedException ie) {
          // ignore/reset
          Thread.currentThread().interrupt();
        }
      }
      if (t != null)
        System.out.println(t);
    }
  }</code>

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 true. This method should in general be called before the pool is actively used.

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.

Method invoked prior to executing the given Runnable in the given thread. This method is invoked by thread t that will execute task 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 super.beforeExecute at the end of this method.

Invokes shutdown when this executor is no longer referenced and it has no threads.

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

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.

Returns the core number of threads.

Returns the thread keep-alive time, which is the amount of time that threads may remain idle before being terminated. Threads that wait this amount of time without processing a task will be terminated if there are more than the core number of threads currently in the pool, or if this pool allows core thread timeout.

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

Returns the maximum allowed number of threads.

Returns the current number of threads in the pool.

Returns the current handler for unexecutable tasks.

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.

Returns the thread factory used to create new threads.

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 true reported a sufficient period after shutdown may indicate that submitted tasks have ignored or suppressed interruption, causing this executor not to properly terminate.

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.

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 false if all core threads have already been started.

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.

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 submit might be converted into a form that maintains Future status. However, in such cases, method purge may be used to remove those Futures that have been cancelled.

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.

Sets the thread keep-alive time, which is the amount of time that threads may remain idle before being terminated. Threads that wait this amount of time without processing a task will be terminated if there are more than the core number of threads currently in the pool, or if this pool allows core thread timeout. This overrides any value set in the constructor.

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.

Sets a new handler for unexecutable tasks.

Sets the thread factory used to create new threads.

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

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

Blocks until all tasks have completed execution after a shutdown request, or the timeout occurs, or the current thread is interrupted, whichever happens first.

Returns true if this executor has been shut down.

Returns true if all tasks have completed following shut down. Note that isTerminated is never true unless either shutdown or shutdownNow was called first.

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.

Attempts to stop all actively executing tasks, halts the processing of waiting tasks, and returns a list of the tasks that were awaiting execution.

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. For example, typical implementations will cancel via Thread#interrupt, so any task that fails to respond to interrupts may never terminate.

Executes the given command at some time in the future. The command may execute in a new thread, in a pooled thread, or in the calling thread, at the discretion of the Executor implementation.

Returns a RunnableFuture for the given runnable and default value.

Returns a RunnableFuture for the given callable task.