Class TimeScheduler

All Implemented Interfaces:
AutoCloseable, Executor, ExecutorService, ScheduledExecutorService, ThreadManager

public class TimeScheduler extends ScheduledThreadPoolExecutor implements ThreadManager
Fixed-delay invalid input: '&' fixed-rate single thread scheduler

The scheduler supports varying scheduling intervals by asking the task every time for its next preferred scheduling interval. Scheduling can either be fixed-delay or fixed-rate. The notions are borrowed from java.util.Timer and retain the same meaning. I.e. in fixed-delay scheduling, the task's new schedule is calculated as:
new_schedule = time_task_starts + scheduling_interval

In fixed-rate scheduling, the next schedule is calculated as:
new_schedule = time_task_was_supposed_to_start + scheduling_interval

The scheduler internally holds a queue of tasks sorted in ascending order according to their next execution time. A task is removed from the queue if it is cancelled, i.e. if TimeScheduler.Task.isCancelled() returns true.

The scheduler internally uses a java.util.SortedSet to keep tasks sorted. java.util.Timer uses an array arranged as a binary heap that doesn't shrink. It is likely that the latter arrangement is faster.

Initially, the scheduler is in SUSPENDed mode, start() need not be called: if a task is added, the scheduler gets started automatically. Calling start() starts the scheduler if it's suspended or stopped else has no effect. Once stop() is called, added tasks will not restart it: start() has to be called to restart the scheduler.

Version:
$Id: TimeScheduler.java,v 1.23.4.4 2008/06/19 15:36:28 vlada Exp $
Author:
Bela Ban
  • Field Details

    • log

      protected static final org.apache.commons.logging.Log log
  • Constructor Details

    • TimeScheduler

      public TimeScheduler()
      Create a scheduler that executes tasks in dynamically adjustable intervals
    • TimeScheduler

      public TimeScheduler(ThreadFactory factory)
    • TimeScheduler

      public TimeScheduler(ThreadFactory factory, int max_threads)
    • TimeScheduler

      public TimeScheduler(int corePoolSize)
  • Method Details

    • getThreadDecorator

      public ThreadDecorator getThreadDecorator()
      Description copied from interface: ThreadManager
      Gets the ThreadDecorator associated with this manager.
      Specified by:
      getThreadDecorator in interface ThreadManager
      Returns:
      the ThreadDecorator, or null if there is none.
    • setThreadDecorator

      public void setThreadDecorator(ThreadDecorator threadDecorator)
      Description copied from interface: ThreadManager
      Sets the ThreadDecorator associated this manager should use.
      Specified by:
      setThreadDecorator in interface ThreadManager
      Parameters:
      threadDecorator - the ThreadDecorator, or null.
    • dumpTaskQueue

      public String dumpTaskQueue()
    • scheduleWithDynamicInterval

      public ScheduledFuture<?> scheduleWithDynamicInterval(TimeScheduler.Task task, boolean relative)
      Schedule a task for execution at varying intervals. After execution, the task will get rescheduled after TimeScheduler.Task.nextInterval() milliseconds. The task is neve done until nextInterval() return a value invalid input: '<'= 0 or the task is cancelled.
      Parameters:
      task - the task to execute
      relative - scheduling scheme: true:
      Task is rescheduled relative to the last time it actually started execution

      false:
      Task is scheduled relative to its last execution schedule. This has the effect that the time between two consecutive executions of the task remains the same.

      Note that relative is always true; we always schedule the next execution relative to the last *actual* (not scheduled) execution

    • scheduleWithDynamicInterval

      public ScheduledFuture<?> scheduleWithDynamicInterval(TimeScheduler.Task t)
      Add a task for execution at adjustable intervals
      Parameters:
      t - the task to execute
    • size

      public int size()
      Answers the number of tasks currently in the queue.
      Returns:
      The number of tasks currently in the queue.
    • start

      public void start()
      Start the scheduler, if it's suspended or stopped
    • stop

      public void stop() throws InterruptedException
      Stop the scheduler if it's running. Switch to stopped, if it's suspended. Clear the task queue, cancelling all un-executed tasks
      Throws:
      InterruptedException - if interrupted while waiting for thread to return
    • afterExecute

      protected void afterExecute(Runnable r, Throwable t)
      Overrides:
      afterExecute in class ThreadPoolExecutor