+++ /dev/null
-/* Timer.java -- Timer that runs TimerTasks at a later time.
- Copyright (C) 2000, 2001 Free Software Foundation, Inc.
-
-This file is part of GNU Classpath.
-
-GNU Classpath is free software; you can redistribute it and/or modify
-it under the terms of the GNU General Public License as published by
-the Free Software Foundation; either version 2, or (at your option)
-any later version.
-
-GNU Classpath is distributed in the hope that it will be useful, but
-WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
-General Public License for more details.
-
-You should have received a copy of the GNU General Public License
-along with GNU Classpath; see the file COPYING. If not, write to the
-Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
-02111-1307 USA.
-
-Linking this library statically or dynamically with other modules is
-making a combined work based on this library. Thus, the terms and
-conditions of the GNU General Public License cover the whole
-combination.
-
-As a special exception, the copyright holders of this library give you
-permission to link this library with independent modules to produce an
-executable, regardless of the license terms of these independent
-modules, and to copy and distribute the resulting executable under
-terms of your choice, provided that you also meet, for each linked
-independent module, the terms and conditions of the license of that
-module. An independent module is a module which is not derived from
-or based on this library. If you modify this library, you may extend
-this exception to your version of the library, but you are not
-obligated to do so. If you do not wish to do so, delete this
-exception statement from your version. */
-
-package java.util;
-
-/**
- * Timer that can run TimerTasks at a later time.
- * TimerTasks can be scheduled for one time execution at some time in the
- * future. They can be scheduled to be rescheduled at a time period after the
- * task was last executed. Or they can be scheduled to be executed repeatedly
- * at a fixed rate.
- * <p>
- * The normal scheduling will result in a more or less even delay in time
- * between successive executions, but the executions could drift in time if
- * the task (or other tasks) takes a long time to execute. Fixed delay
- * scheduling guarantees more or less that the task will be executed at a
- * specific time, but if there is ever a delay in execution then the period
- * between successive executions will be shorter. The first method of
- * repeated scheduling is preferred for repeated tasks in response to user
- * interaction, the second method of repeated scheduling is preferred for tasks
- * that act like alarms.
- * <p>
- * The Timer keeps a binary heap as a task priority queue which means that
- * scheduling and serving of a task in a queue of n tasks costs O(log n).
- *
- * @see TimerTask
- * @since 1.3
- * @author Mark Wielaard (mark@klomp.org)
- */
-public class Timer
-{
- /**
- * Priority Task Queue.
- * TimerTasks are kept in a binary heap.
- * The scheduler calls sleep() on the queue when it has nothing to do or
- * has to wait. A sleeping scheduler can be notified by calling interrupt()
- * which is automatically called by the enqueue(), cancel() and
- * timerFinalized() methods.
- */
- private static final class TaskQueue
- {
- /** Default size of this queue */
- private final int DEFAULT_SIZE = 32;
-
- /** Whether to return null when there is nothing in the queue */
- private boolean nullOnEmpty;
-
- /**
- * The heap containing all the scheduled TimerTasks
- * sorted by the TimerTask.scheduled field.
- * Null when the stop() method has been called.
- */
- private TimerTask heap[];
-
- /**
- * The actual number of elements in the heap
- * Can be less then heap.length.
- * Note that heap[0] is used as a sentinel.
- */
- private int elements;
-
- /**
- * Creates a TaskQueue of default size without any elements in it.
- */
- public TaskQueue()
- {
- heap = new TimerTask[DEFAULT_SIZE];
- elements = 0;
- nullOnEmpty = false;
- }
-
- /**
- * Adds a TimerTask at the end of the heap.
- * Grows the heap if necessary by doubling the heap in size.
- */
- private void add(TimerTask task)
- {
- elements++;
- if (elements == heap.length)
- {
- TimerTask new_heap[] = new TimerTask[heap.length * 2];
- System.arraycopy(heap, 0, new_heap, 0, heap.length);
- heap = new_heap;
- }
- heap[elements] = task;
- }
-
- /**
- * Removes the last element from the heap.
- * Shrinks the heap in half if
- * elements+DEFAULT_SIZE/2 <= heap.length/4.
- */
- private void remove()
- {
- // clear the entry first
- heap[elements] = null;
- elements--;
- if (elements + DEFAULT_SIZE / 2 <= (heap.length / 4))
- {
- TimerTask new_heap[] = new TimerTask[heap.length / 2];
- System.arraycopy(heap, 0, new_heap, 0, elements + 1);
- heap = new_heap;
- }
- }
-
- /**
- * Adds a task to the queue and puts it at the correct place
- * in the heap.
- */
- public synchronized void enqueue(TimerTask task)
- {
- // Check if it is legal to add another element
- if (heap == null)
- {
- throw new IllegalStateException
- ("cannot enqueue when stop() has been called on queue");
- }
-
- heap[0] = task; // sentinel
- add(task); // put the new task at the end
- // Now push the task up in the heap until it has reached its place
- int child = elements;
- int parent = child / 2;
- while (heap[parent].scheduled > task.scheduled)
- {
- heap[child] = heap[parent];
- child = parent;
- parent = child / 2;
- }
- // This is the correct place for the new task
- heap[child] = task;
- heap[0] = null; // clear sentinel
- // Maybe sched() is waiting for a new element
- this.notify();
- }
-
- /**
- * Returns the top element of the queue.
- * Can return null when no task is in the queue.
- */
- private TimerTask top()
- {
- if (elements == 0)
- {
- return null;
- }
- else
- {
- return heap[1];
- }
- }
-
- /**
- * Returns the top task in the Queue.
- * Removes the element from the heap and reorders the heap first.
- * Can return null when there is nothing in the queue.
- */
- public synchronized TimerTask serve()
- {
- // The task to return
- TimerTask task = null;
-
- while (task == null)
- {
- // Get the next task
- task = top();
-
- // return null when asked to stop
- // or if asked to return null when the queue is empty
- if ((heap == null) || (task == null && nullOnEmpty))
- {
- return null;
- }
-
- // Do we have a task?
- if (task != null)
- {
- // The time to wait until the task should be served
- long time = task.scheduled - System.currentTimeMillis();
- if (time > 0)
- {
- // This task should not yet be served
- // So wait until this task is ready
- // or something else happens to the queue
- task = null; // set to null to make sure we call top()
- try
- {
- this.wait(time);
- }
- catch (InterruptedException _)
- {
- }
- }
- }
- else
- {
- // wait until a task is added
- // or something else happens to the queue
- try
- {
- this.wait();
- }
- catch (InterruptedException _)
- {
- }
- }
- }
-
- // reconstruct the heap
- TimerTask lastTask = heap[elements];
- remove();
-
- // drop lastTask at the beginning and move it down the heap
- int parent = 1;
- int child = 2;
- heap[1] = lastTask;
- while (child <= elements)
- {
- if (child < elements)
- {
- if (heap[child].scheduled > heap[child + 1].scheduled)
- {
- child++;
- }
- }
-
- if (lastTask.scheduled <= heap[child].scheduled)
- break; // found the correct place (the parent) - done
-
- heap[parent] = heap[child];
- parent = child;
- child = parent * 2;
- }
-
- // this is the correct new place for the lastTask
- heap[parent] = lastTask;
-
- // return the task
- return task;
- }
-
- /**
- * When nullOnEmpty is true the serve() method will return null when
- * there are no tasks in the queue, otherwise it will wait until
- * a new element is added to the queue. It is used to indicate to
- * the scheduler that no new tasks will ever be added to the queue.
- */
- public synchronized void setNullOnEmpty(boolean nullOnEmpty)
- {
- this.nullOnEmpty = nullOnEmpty;
- this.notify();
- }
-
- /**
- * When this method is called the current and all future calls to
- * serve() will return null. It is used to indicate to the Scheduler
- * that it should stop executing since no more tasks will come.
- */
- public synchronized void stop()
- {
- this.heap = null;
- this.elements = 0;
- this.notify();
- }
-
- } // TaskQueue
-
- /**
- * The scheduler that executes all the tasks on a particular TaskQueue,
- * reschedules any repeating tasks and that waits when no task has to be
- * executed immediatly. Stops running when canceled or when the parent
- * Timer has been finalized and no more tasks have to be executed.
- */
- private static final class Scheduler implements Runnable
- {
- // The priority queue containing all the TimerTasks.
- private TaskQueue queue;
-
- /**
- * Creates a new Scheduler that will schedule the tasks on the
- * given TaskQueue.
- */
- public Scheduler(TaskQueue queue)
- {
- this.queue = queue;
- }
-
- public void run()
- {
- TimerTask task;
- while ((task = queue.serve()) != null)
- {
- // If this task has not been canceled
- if (task.scheduled >= 0)
- {
-
- // Mark execution time
- task.lastExecutionTime = task.scheduled;
-
- // Repeatable task?
- if (task.period < 0)
- {
- // Last time this task is executed
- task.scheduled = -1;
- }
-
- // Run the task
- try
- {
- task.run();
- }
- catch (Throwable t)
- {
- /* ignore all errors */
- }
- }
-
- // Calculate next time and possibly re-enqueue.
- if (task.scheduled >= 0)
- {
- if (task.fixed)
- {
- task.scheduled += task.period;
- }
- else
- {
- task.scheduled = task.period + System.currentTimeMillis();
- }
-
- try
- {
- queue.enqueue(task);
- }
- catch (IllegalStateException ise)
- {
- // Ignore. Apparently the Timer queue has been stopped.
- }
- }
- }
- }
- } // Scheduler
-
- // Number of Timers created.
- // Used for creating nice Thread names.
- private static int nr = 0;
-
- // The queue that all the tasks are put in.
- // Given to the scheduler
- private TaskQueue queue;
-
- // The Scheduler that does all the real work
- private Scheduler scheduler;
-
- // Used to run the scheduler.
- // Also used to checked if the Thread is still running by calling
- // thread.isAlive(). Sometimes a Thread is suddenly killed by the system
- // (if it belonged to an Applet).
- private Thread thread;
-
- // When cancelled we don't accept any more TimerTasks.
- private boolean canceled;
-
- /**
- * Creates a new Timer with a non daemon Thread as Scheduler, with normal
- * priority and a default name.
- */
- public Timer()
- {
- this(false);
- }
-
- /**
- * Creates a new Timer with a daemon Thread as scheduler if daemon is true,
- * with normal priority and a default name.
- */
- public Timer(boolean daemon)
- {
- this(daemon, Thread.NORM_PRIORITY);
- }
-
- /**
- * Creates a new Timer with a daemon Thread as scheduler if daemon is true,
- * with the priority given and a default name.
- */
- private Timer(boolean daemon, int priority)
- {
- this(daemon, priority, "Timer-" + (++nr));
- }
-
- /**
- * Creates a new Timer with a daemon Thread as scheduler if daemon is true,
- * with the priority and name given.E
- */
- private Timer(boolean daemon, int priority, String name)
- {
- canceled = false;
- queue = new TaskQueue();
- scheduler = new Scheduler(queue);
- thread = new Thread(scheduler, name);
- thread.setDaemon(daemon);
- thread.setPriority(priority);
- thread.start();
- }
-
- /**
- * Cancels the execution of the scheduler. If a task is executing it will
- * normally finish execution, but no other tasks will be executed and no
- * more tasks can be scheduled.
- */
- public void cancel()
- {
- canceled = true;
- queue.stop();
- }
-
- /**
- * Schedules the task at Time time, repeating every period
- * milliseconds if period is positive and at a fixed rate if fixed is true.
- *
- * @exception IllegalArgumentException if time is negative
- * @exception IllegalStateException if the task was already scheduled or
- * canceled or this Timer is canceled or the scheduler thread has died
- */
- private void schedule(TimerTask task, long time, long period, boolean fixed)
- {
- if (time < 0)
- throw new IllegalArgumentException("negative time");
-
- if (task.scheduled == 0 && task.lastExecutionTime == -1)
- {
- task.scheduled = time;
- task.period = period;
- task.fixed = fixed;
- }
- else
- {
- throw new IllegalStateException
- ("task was already scheduled or canceled");
- }
-
- if (!this.canceled && this.thread != null)
- {
- queue.enqueue(task);
- }
- else
- {
- throw new IllegalStateException
- ("timer was canceled or scheduler thread has died");
- }
- }
-
- private static void positiveDelay(long delay)
- {
- if (delay < 0)
- {
- throw new IllegalArgumentException("delay is negative");
- }
- }
-
- private static void positivePeriod(long period)
- {
- if (period < 0)
- {
- throw new IllegalArgumentException("period is negative");
- }
- }
-
- /**
- * Schedules the task at the specified data for one time execution.
- *
- * @exception IllegalArgumentException if date.getTime() is negative
- * @exception IllegalStateException if the task was already scheduled or
- * canceled or this Timer is canceled or the scheduler thread has died
- */
- public void schedule(TimerTask task, Date date)
- {
- long time = date.getTime();
- schedule(task, time, -1, false);
- }
-
- /**
- * Schedules the task at the specified date and reschedules the task every
- * period milliseconds after the last execution of the task finishes until
- * this timer or the task is canceled.
- *
- * @exception IllegalArgumentException if period or date.getTime() is
- * negative
- * @exception IllegalStateException if the task was already scheduled or
- * canceled or this Timer is canceled or the scheduler thread has died
- */
- public void schedule(TimerTask task, Date date, long period)
- {
- positivePeriod(period);
- long time = date.getTime();
- schedule(task, time, period, false);
- }
-
- /**
- * Schedules the task after the specified delay milliseconds for one time
- * execution.
- *
- * @exception IllegalArgumentException if delay or
- * System.currentTimeMillis + delay is negative
- * @exception IllegalStateException if the task was already scheduled or
- * canceled or this Timer is canceled or the scheduler thread has died
- */
- public void schedule(TimerTask task, long delay)
- {
- positiveDelay(delay);
- long time = System.currentTimeMillis() + delay;
- schedule(task, time, -1, false);
- }
-
- /**
- * Schedules the task after the delay milliseconds and reschedules the
- * task every period milliseconds after the last execution of the task
- * finishes until this timer or the task is canceled.
- *
- * @exception IllegalArgumentException if delay or period is negative
- * @exception IllegalStateException if the task was already scheduled or
- * canceled or this Timer is canceled or the scheduler thread has died
- */
- public void schedule(TimerTask task, long delay, long period)
- {
- positiveDelay(delay);
- positivePeriod(period);
- long time = System.currentTimeMillis() + delay;
- schedule(task, time, period, false);
- }
-
- /**
- * Schedules the task at the specified date and reschedules the task at a
- * fixed rate every period milliseconds until this timer or the task is
- * canceled.
- *
- * @exception IllegalArgumentException if period or date.getTime() is
- * negative
- * @exception IllegalStateException if the task was already scheduled or
- * canceled or this Timer is canceled or the scheduler thread has died
- */
- public void scheduleAtFixedRate(TimerTask task, Date date, long period)
- {
- positivePeriod(period);
- long time = date.getTime();
- schedule(task, time, period, true);
- }
-
- /**
- * Schedules the task after the delay milliseconds and reschedules the task
- * at a fixed rate every period milliseconds until this timer or the task
- * is canceled.
- *
- * @exception IllegalArgumentException if delay or
- * System.currentTimeMillis + delay is negative
- * @exception IllegalStateException if the task was already scheduled or
- * canceled or this Timer is canceled or the scheduler thread has died
- */
- public void scheduleAtFixedRate(TimerTask task, long delay, long period)
- {
- positiveDelay(delay);
- positivePeriod(period);
- long time = System.currentTimeMillis() + delay;
- schedule(task, time, period, true);
- }
-
- /**
- * Tells the scheduler that the Timer task died
- * so there will be no more new tasks scheduled.
- */
- protected void finalize()
- {
- queue.setNullOnEmpty(true);
- }
-}
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