Modifier and Type	Class and Description
protected class	HsqlTimer.Task Encapsulates a Runnable and its scheduling attributes.
protected static class	HsqlTimer.TaskQueue Heap-based priority queue.
protected class	HsqlTimer.TaskRunner The Runnable that the background thread uses to execute scheduled tasks.

Modifier and Type	Field and Description
pack-priv volatile boolean	isShutdown Whether this timer should disallow all further processing.
pack-priv static int	nowCount stats var
pack-priv final HsqlTimer.TaskQueue	taskQueue The priority queue for the scheduled tasks.
pack-priv final HsqlTimer.TaskRunner	taskRunner The inner runnable that executes tasks in the background thread.
pack-priv Thread	taskRunnerThread The background thread.
pack-priv final ThreadFactory	threadFactory The factory that produces the background threads.

Access	Constructor and Description
public	HsqlTimer() Constructs a new HsqlTimer using the default thread factory implementation.
public	HsqlTimer(final ThreadFactory the ThreadFactory used to produce this timer's background threads. If null, the default implementation supplied by this class will be used. threadFactory) Constructs a new HsqlTimer.

Method Summary

Modifier and Type	Method and Description
pack-priv HsqlTimer.Task	Returns: an opaque reference to the internal task addTask(final long the time of the task's first execution first, final Runnable the Runnable to execute runnable, final long the task's periodicity period, boolean if true, use fixed rate else use fixed delay scheduling relative) Adds to the task queue a new Task object encapsulating the supplied Runnable and scheduling arguments.
public static void	cancel(final Object a task reference task) Causes the task referenced by the supplied argument to be cancelled.
pack-priv synchronized void	clearThread() Sets the background thread to null.
public int	Returns: `0 if equal, < 0 if a < b, > 0 if a > b` compare(final Object the first Task a, final Object the second Task b) Implements java.util.Comparator.compare. Required to back the priority queue for scheduled tasks.
public static Date	Returns: the last time the referenced task was executed; null if never getLastScheduled(Object a task reference task) Retrieves the last time the referenced task was executed, as a Date object.
public static Date	Returns: the next time the referenced task is due to be executed getNextScheduled(Object a task reference task) Retrieves the next time the referenced task is due to be executed, as a Date object.
public synchronized Thread	Returns: the current background thread (may be null) getThread() Retrieves the background execution thread.
public static boolean	Returns: true if referenced task is cancelled isCancelled(final Object a task reference task) Retrieves whether the specified argument references a cancelled task.
public static boolean	Returns: true if the reference is scheduled using a fixed delay isFixedDelay(final Object a task reference task) Retrieves whether the specified argument references a task scheduled periodically using fixed delay scheduling.
public static boolean	Returns: true if the task is scheduled at a fixed rate isFixedRate(final Object a task reference task) Retrieves whether the specified argument references a task scheduled periodically using fixed rate scheduling.
public static boolean	Returns: true if the task is scheduled for periodic execution isPeriodic(final Object a task reference task) Retrieves whether the specified argument references a task scheduled for periodic execution.
public Thread	Returns: a new Thread constructed from the designated runnable. newThread(final Runnable used to construct the new Thread. runnable) Implements org.hsqldb.lib.ThreadFactory.newThread. Default ThreadFactory implementation.
pack-priv HsqlTimer.Task	Returns: the next task to execute, or null nextTask() Retrieves the next task to execute, or null if this timer is shutdown, the current thread is interrupted, or there are no queued tasks.
pack-priv static long	Returns: System.currentTimeMillis() now() Convenience method replacing the longer incantation: System.currentTimeMillis()
public synchronized void	restart() (Re)starts background processing of the task queue.
public Object	Returns: opaque reference to the internal task scheduleAfter(final long in milliseconds delay, final Runnable the Runnable to execute. runnable) Causes the specified Runnable to be executed once in the background after the specified delay.
public Object	Returns: opaque reference to the internal task scheduleAt(final Date time at which to execute the specified Runnable date, final Runnable the Runnable to execute. runnable) Causes the specified Runnable to be executed once in the background at the specified time.
public Object	Returns: opaque reference to the internal task schedulePeriodicallyAfter(final long in milliseconds delay, final long the cycle period period, final Runnable the Runnable to execute. runnable, final boolean if true, fixed rate scheduling else fixed delay scheduling relative) Causes the specified Runnable to be executed periodically in the background, starting after the specified delay.
public Object	Returns: opaque reference to the internal task schedulePeriodicallyAt(final Date time at which to execute the specified Runnable date, final long the cycle period period, final Runnable the Runnable to execute runnable, final boolean if true, fixed rate scheduling else fixed delay scheduling relative) Causes the specified Runnable to be executed periodically in the background, starting at the specified time.
public static Object	Returns: a task reference, as per the rules stated above. setPeriod(final Object the task whose periodicity is to be set task, final long the new period period) Sets the periodicity of the designated task to a new value.
public synchronized void	shutdown() Shuts down this timer after the current task (if any) completes.
public synchronized void	shutDown() for compatibility with previous version
public synchronized void	shutdownImmediately() Shuts down this timer immediately, interrupting the wait state associated with the current head of the task queue or the wait state internal to the currently executing task, if any such state is currently in effect.

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

Field Detail

isShutdown	back to summary
pack-priv volatile boolean isShutdown Whether this timer should disallow all further processing. Once set true, stays true forever.

nowCount	back to summary
pack-priv static int nowCount stats var

taskQueue	back to summary
pack-priv final HsqlTimer.TaskQueue taskQueue The priority queue for the scheduled tasks.

taskRunner	back to summary
pack-priv final HsqlTimer.TaskRunner taskRunner The inner runnable that executes tasks in the background thread.

taskRunnerThread	back to summary
pack-priv Thread taskRunnerThread The background thread.

threadFactory	back to summary
pack-priv final ThreadFactory threadFactory The factory that produces the background threads.

Constructor Detail

HsqlTimer	back to summary
public HsqlTimer() Constructs a new HsqlTimer using the default thread factory implementation.

HsqlTimer	back to summary
public HsqlTimer(final ThreadFactory threadFactory) Constructs a new HsqlTimer. Uses the specified thread factory implementation. Parameters threadFactory:ThreadFactory the ThreadFactory used to produce this timer's background threads. If null, the default implementation supplied by this class will be used.

HsqlTimer

back to summary

public HsqlTimer(final ThreadFactory threadFactory)

Constructs a new HsqlTimer. Uses the specified thread factory implementation.

Parameters

threadFactory:ThreadFactory: the ThreadFactory used to produce this timer's background threads. If null, the default implementation supplied by this class will be used.

Method Detail

addTask	back to summary
pack-priv HsqlTimer.Task addTask(final long first, final Runnable runnable, final long period, boolean relative) Adds to the task queue a new Task object encapsulating the supplied Runnable and scheduling arguments. Parameters first:long the time of the task's first execution runnable:Runnable the Runnable to execute period:long the task's periodicity relative:boolean if true, use fixed rate else use fixed delay scheduling Returns:HsqlTimer.Task an opaque reference to the internal task

addTask

back to summary

pack-priv HsqlTimer.Task addTask(final long first, final Runnable runnable, final long period, boolean relative)

Adds to the task queue a new Task object encapsulating the supplied Runnable and scheduling arguments.

Parameters

first:long: the time of the task's first execution
runnable:Runnable: the Runnable to execute
period:long: the task's periodicity
relative:boolean: if true, use fixed rate else use fixed delay scheduling

Returns:HsqlTimer.Task

an opaque reference to the internal task

cancel	back to summary
public static void cancel(final Object task) Causes the task referenced by the supplied argument to be cancelled. If the referenced task is currently executing, it will continue until finished but will not be rescheduled. Parameters task:Object a task reference

cancel

back to summary

public static void cancel(final Object task)

Causes the task referenced by the supplied argument to be cancelled. If the referenced task is currently executing, it will continue until finished but will not be rescheduled.

Parameters

task:Object: a task reference

clearThread	back to summary
pack-priv synchronized void clearThread() Sets the background thread to null.

compare back to summary

compare	back to summary
public int compare(final Object a, final Object b) Implements java.util.Comparator.compare. Required to back the priority queue for scheduled tasks. Parameters a:Object the first Task b:Object the second Task Returns:int `0 if equal, < 0 if a < b, > 0 if a > b`

public int compare(final Object a, final Object b)

Implements java.util.Comparator.compare.

Required to back the priority queue for scheduled tasks.

Parameters

a:Object: the first Task
b:Object: the second Task

Returns:int

0 if equal, < 0 if a < b, > 0 if a > b

getLastScheduled	back to summary
public static Date getLastScheduled(Object task) Retrieves the last time the referenced task was executed, as a Date object. If the task has never been executed, null is returned. Parameters task:Object a task reference Returns:Date the last time the referenced task was executed; null if never

getLastScheduled

back to summary

public static Date getLastScheduled(Object task)

Retrieves the last time the referenced task was executed, as a Date object. If the task has never been executed, null is returned.

Parameters

task:Object: a task reference

Returns:Date

the last time the referenced task was executed; null if never

getNextScheduled	back to summary
public static Date getNextScheduled(Object task) Retrieves the next time the referenced task is due to be executed, as a Date object. If the referenced task is cancelled, null is returned. Parameters task:Object a task reference Returns:Date the next time the referenced task is due to be executed

getNextScheduled

back to summary

public static Date getNextScheduled(Object task)

Retrieves the next time the referenced task is due to be executed, as a Date object. If the referenced task is cancelled, null is returned.

Parameters

task:Object: a task reference

Returns:Date

the next time the referenced task is due to be executed

getThread	back to summary
public synchronized Thread getThread() Retrieves the background execution thread. null is returned if there is no such thread. Returns:Thread the current background thread (may be null)

getThread

back to summary

public synchronized Thread getThread()

Retrieves the background execution thread.

null is returned if there is no such thread.

Returns:Thread: the current background thread (may be null)

isCancelled	back to summary
public static boolean isCancelled(final Object task) Retrieves whether the specified argument references a cancelled task. Parameters task:Object a task reference Returns:boolean true if referenced task is cancelled

isCancelled

back to summary

public static boolean isCancelled(final Object task)

Retrieves whether the specified argument references a cancelled task.

Parameters

task:Object: a task reference

Returns:boolean

true if referenced task is cancelled

isFixedDelay	back to summary
public static boolean isFixedDelay(final Object task) Retrieves whether the specified argument references a task scheduled periodically using fixed delay scheduling. Parameters task:Object a task reference Returns:boolean true if the reference is scheduled using a fixed delay

isFixedDelay

back to summary

public static boolean isFixedDelay(final Object task)

Retrieves whether the specified argument references a task scheduled periodically using fixed delay scheduling.

Parameters

task:Object: a task reference

Returns:boolean

true if the reference is scheduled using a fixed delay

isFixedRate	back to summary
public static boolean isFixedRate(final Object task) Retrieves whether the specified argument references a task scheduled periodically using fixed rate scheduling. Parameters task:Object a task reference Returns:boolean true if the task is scheduled at a fixed rate

isFixedRate

back to summary

public static boolean isFixedRate(final Object task)

Retrieves whether the specified argument references a task scheduled periodically using fixed rate scheduling.

Parameters

task:Object: a task reference

Returns:boolean

true if the task is scheduled at a fixed rate

isPeriodic	back to summary
public static boolean isPeriodic(final Object task) Retrieves whether the specified argument references a task scheduled for periodic execution. Parameters task:Object a task reference Returns:boolean true if the task is scheduled for periodic execution

isPeriodic

back to summary

public static boolean isPeriodic(final Object task)

Retrieves whether the specified argument references a task scheduled for periodic execution.

Parameters

task:Object: a task reference

Returns:boolean

true if the task is scheduled for periodic execution

newThread	back to summary
public Thread newThread(final Runnable runnable) Implements org.hsqldb.lib.ThreadFactory.newThread. Default ThreadFactory implementation. Constructs a new Thread from the designated runnable, sets its name to "HSQLDB Timer @" + Integer.toHexString(hashCode()), and sets it as a daemon thread. Parameters runnable:Runnable used to construct the new Thread. Returns:Thread a new Thread constructed from the designated runnable.

newThread

back to summary

public Thread newThread(final Runnable runnable)

Implements org.hsqldb.lib.ThreadFactory.newThread.

Default ThreadFactory implementation.

Constructs a new Thread from the designated runnable, sets its name to "HSQLDB Timer @" + Integer.toHexString(hashCode()), and sets it as a daemon thread.

Parameters

runnable:Runnable: used to construct the new Thread.

Returns:Thread

a new Thread constructed from the designated runnable.

nextTask	back to summary
pack-priv HsqlTimer.Task nextTask() Retrieves the next task to execute, or null if this timer is shutdown, the current thread is interrupted, or there are no queued tasks. Returns:HsqlTimer.Task the next task to execute, or null

nextTask

back to summary

pack-priv HsqlTimer.Task nextTask()

Retrieves the next task to execute, or null if this timer is shutdown, the current thread is interrupted, or there are no queued tasks.

Returns:HsqlTimer.Task: the next task to execute, or null

now	back to summary
pack-priv static long now() Convenience method replacing the longer incantation: System.currentTimeMillis() Returns:long System.currentTimeMillis()

now

back to summary

pack-priv static long now()

Convenience method replacing the longer incantation: System.currentTimeMillis()

Returns:long: System.currentTimeMillis()

restart back to summary

restart	back to summary
public synchronized void restart() throws IllegalStateException (Re)starts background processing of the task queue. Exceptions IllegalStateException: if this timer is shut down. See Also `shutdown()`, `shutdownImmediately()`

public synchronized void restart() throws IllegalStateException

(Re)starts background processing of the task queue.

Exceptions

IllegalStateException:: if this timer is shut down.

See Also

shutdown(), shutdownImmediately()

scheduleAfter	back to summary
public Object scheduleAfter(final long delay, final Runnable runnable) throws IllegalArgumentException Causes the specified Runnable to be executed once in the background after the specified delay. Parameters delay:long in milliseconds runnable:Runnable the Runnable to execute. Returns:Object opaque reference to the internal task Exceptions IllegalArgumentException: if runnable is null

scheduleAfter

back to summary

public Object scheduleAfter(final long delay, final Runnable runnable) throws IllegalArgumentException

Causes the specified Runnable to be executed once in the background after the specified delay.

Parameters

delay:long: in milliseconds
runnable:Runnable: the Runnable to execute.

Returns:Object

opaque reference to the internal task

Exceptions

IllegalArgumentException:: if runnable is null

scheduleAt	back to summary
public Object scheduleAt(final Date date, final Runnable runnable) throws IllegalArgumentException Causes the specified Runnable to be executed once in the background at the specified time. Parameters date:Date time at which to execute the specified Runnable runnable:Runnable the Runnable to execute. Returns:Object opaque reference to the internal task Exceptions IllegalArgumentException: if date or runnable is null

scheduleAt

back to summary

public Object scheduleAt(final Date date, final Runnable runnable) throws IllegalArgumentException

Causes the specified Runnable to be executed once in the background at the specified time.

Parameters

date:Date: time at which to execute the specified Runnable
runnable:Runnable: the Runnable to execute.

Returns:Object

opaque reference to the internal task

Exceptions

IllegalArgumentException:: if date or runnable is null

schedulePeriodicallyAfter back to summary

schedulePeriodicallyAfter	back to summary
public Object schedulePeriodicallyAfter(final long delay, final long period, final Runnable runnable, final boolean relative) throws IllegalArgumentException Causes the specified Runnable to be executed periodically in the background, starting after the specified delay. Parameters delay:long in milliseconds period:long the cycle period runnable:Runnable the Runnable to execute. relative:boolean if true, fixed rate scheduling else fixed delay scheduling Returns:Object opaque reference to the internal task Exceptions IllegalArgumentException: if runnable is null or period is `<= 0`

public Object schedulePeriodicallyAfter(final long delay, final long period, final Runnable runnable, final boolean relative) throws IllegalArgumentException

Causes the specified Runnable to be executed periodically in the background, starting after the specified delay.

Parameters

delay:long: in milliseconds
period:long: the cycle period
runnable:Runnable: the Runnable to execute.
relative:boolean: if true, fixed rate scheduling else fixed delay scheduling

Returns:Object

opaque reference to the internal task

Exceptions

IllegalArgumentException:: if runnable is null or period is <= 0

schedulePeriodicallyAt back to summary

schedulePeriodicallyAt	back to summary
public Object schedulePeriodicallyAt(final Date date, final long period, final Runnable runnable, final boolean relative) throws IllegalArgumentException Causes the specified Runnable to be executed periodically in the background, starting at the specified time. Parameters date:Date time at which to execute the specified Runnable period:long the cycle period runnable:Runnable the Runnable to execute relative:boolean if true, fixed rate scheduling else fixed delay scheduling Returns:Object opaque reference to the internal task Exceptions IllegalArgumentException: if date or runnable is null, or period is `<= 0`

public Object schedulePeriodicallyAt(final Date date, final long period, final Runnable runnable, final boolean relative) throws IllegalArgumentException

Causes the specified Runnable to be executed periodically in the background, starting at the specified time.

Parameters

date:Date: time at which to execute the specified Runnable
period:long: the cycle period
runnable:Runnable: the Runnable to execute
relative:boolean: if true, fixed rate scheduling else fixed delay scheduling

Returns:Object

opaque reference to the internal task

Exceptions

IllegalArgumentException:: if date or runnable is null, or period is <= 0

setPeriod	back to summary
public static Object setPeriod(final Object task, final long period) Sets the periodicity of the designated task to a new value. If the designated task is cancelled or the new period is identical to the task's current period, then this invocation has essentially no effect and the submitted object is returned. Otherwise, if the new period is greater than the designated task's current period, then a simple assignment occurs and the submitted object is returned. If neither case holds, then the designated task is cancelled and a new, equivalent task with the new period is scheduled for immediate first execution and returned to the caller. Parameters task:Object the task whose periodicity is to be set period:long the new period Returns:Object a task reference, as per the rules stated above.

setPeriod

back to summary

public static Object setPeriod(final Object task, final long period)

Sets the periodicity of the designated task to a new value.

If the designated task is cancelled or the new period is identical to the task's current period, then this invocation has essentially no effect and the submitted object is returned.

Otherwise, if the new period is greater than the designated task's current period, then a simple assignment occurs and the submitted object is returned.

If neither case holds, then the designated task is cancelled and a new, equivalent task with the new period is scheduled for immediate first execution and returned to the caller.

Parameters

task:Object: the task whose periodicity is to be set
period:long: the new period

Returns:Object

a task reference, as per the rules stated above.

shutdown	back to summary
public synchronized void shutdown() Shuts down this timer after the current task (if any) completes. After this call, the timer has permanently entered the shutdown state; attempting to schedule any new task or directly restart this timer will result in an IllegalStateException.

shutdown

back to summary

public synchronized void shutdown()

Shuts down this timer after the current task (if any) completes.

After this call, the timer has permanently entered the shutdown state; attempting to schedule any new task or directly restart this timer will result in an IllegalStateException.

shutDown	back to summary
public synchronized void shutDown() for compatibility with previous version

shutdownImmediately	back to summary
public synchronized void shutdownImmediately() Shuts down this timer immediately, interrupting the wait state associated with the current head of the task queue or the wait state internal to the currently executing task, if any such state is currently in effect. After this call, the timer has permanently entered the shutdown state; attempting to schedule any new task or directly restart this timer will result in an IllegalStateException. Note If the integrity of work performed by a scheduled task may be adversely affected by an unplanned interruption, it is the responsibility of the task's implementation to deal correctly with the possibility that this method is called while such work is in progress, for instance by catching the InterruptedException, completing the work, and then rethrowing the exception.

shutdownImmediately

back to summary

public synchronized void shutdownImmediately()

Shuts down this timer immediately, interrupting the wait state associated with the current head of the task queue or the wait state internal to the currently executing task, if any such state is currently in effect. After this call, the timer has permanently entered the shutdown state; attempting to schedule any new task or directly restart this timer will result in an IllegalStateException.

Note

If the integrity of work performed by a scheduled task may be adversely affected by an unplanned interruption, it is the responsibility of the task's implementation to deal correctly with the possibility that this method is called while such work is in progress, for instance by catching the InterruptedException, completing the work, and then rethrowing the exception.

org.hsqldb.lib back to summary

protected Class HsqlTimer.Task

Class Inheritance

extends Object

java.lang.Object
org.hsqldb.lib.HsqlTimer.Task

Encapsulates a Runnable and its scheduling attributes. Essentially, a wrapper class used to schedule a Runnable object for execution by the enclosing HsqlTimer's TaskRunner in a background thread.

Field Summary

Modifier and Type	Field and Description
private final Object	cancel_mutex Serializes concurrent access to the cancelled field.
pack-priv boolean	cancelled Whether to silently remove this task instead of running it, the next time (if ever) it makes its way to the head of the timer queue.
pack-priv long	last The time this task was last executed, or 0 if never.
pack-priv long	next The next time this task is scheduled to execute.
pack-priv long	period The periodic interval, or 0 if one-shot.
pack-priv final boolean	relative Scheduling policy flag.
pack-priv Runnable	runnable What to run.

Constructor Summary

Access	Constructor and Description
pack-priv	Task(final long the first time to execute first, final Runnable the Runnable to execute runnable, final long the periodicity of execution period, final boolean if true, use fixed rate scheduling else fixed delay relative) Constructs a new Task object encapsulating the specified Runnable and scheduling arguments.

Method Summary

Modifier and Type	Method and Description
pack-priv void	cancel() Sets this task's cancelled flag true and signals its taskQueue.
pack-priv synchronized long	Returns: the last time this task was executed or zero if never getLastScheduled() Retrieves the instant in time just before this task was last executed by the background thread.
pack-priv synchronized long	Returns: the time at which this task is next scheduled for execution getNextScheduled() Retrieves the time at which this task is next scheduled for execution.
pack-priv boolean	Returns: true if cancelled, else false isCancelled() Retrieves whether this task is cancelled.
pack-priv synchronized Object	Returns: a task reference, as per the rules stated above. setPeriod(final long the new period newPeriod) Sets the new periodicity of this task in milliseconds.
pack-priv synchronized void	updateSchedule(final long when this task was last executed last, final long when this task is to be next executed next) Updates the last and next scheduled execution times.

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

Field Detail

cancel_mutex	back to summary
private final Object cancel_mutex Serializes concurrent access to the cancelled field.

cancelled	back to summary
pack-priv boolean cancelled Whether to silently remove this task instead of running it, the next time (if ever) it makes its way to the head of the timer queue.

last	back to summary
pack-priv long last The time this task was last executed, or 0 if never.

next	back to summary
pack-priv long next The next time this task is scheduled to execute.

period	back to summary
pack-priv long period The periodic interval, or 0 if one-shot.

relative	back to summary
pack-priv final boolean relative Scheduling policy flag. When true, scheduling is fixed rate (as opposed to fixed delay), and schedule updates are calculated relative to when the task was last run rather than a fixed delay starting from the current wall-clock time provided by System.currentTimeMillis(). This helps normalize scheduling for tasks that must attempt to maintain a fixed rate of execution.

relative

back to summary

pack-priv final boolean relative

Scheduling policy flag.

When true, scheduling is fixed rate (as opposed to fixed delay), and schedule updates are calculated relative to when the task was last run rather than a fixed delay starting from the current wall-clock time provided by System.currentTimeMillis().

This helps normalize scheduling for tasks that must attempt to maintain a fixed rate of execution.

runnable	back to summary
pack-priv Runnable runnable What to run.

Constructor Detail

Task	back to summary
pack-priv Task(final long first, final Runnable runnable, final long period, final boolean relative) Constructs a new Task object encapsulating the specified Runnable and scheduling arguments. Parameters first:long the first time to execute runnable:Runnable the Runnable to execute period:long the periodicity of execution relative:boolean if true, use fixed rate scheduling else fixed delay

Task

back to summary

pack-priv Task(final long first, final Runnable runnable, final long period, final boolean relative)

Constructs a new Task object encapsulating the specified Runnable and scheduling arguments.

Parameters

first:long: the first time to execute
runnable:Runnable: the Runnable to execute
period:long: the periodicity of execution
relative:boolean: if true, use fixed rate scheduling else fixed delay

Method Detail

cancel	back to summary
pack-priv void cancel() Sets this task's cancelled flag true and signals its taskQueue.

getLastScheduled	back to summary
pack-priv synchronized long getLastScheduled() Retrieves the instant in time just before this task was last executed by the background thread. A value of zero indicates that this task has never been executed. Returns:long the last time this task was executed or zero if never

getLastScheduled

back to summary

pack-priv synchronized long getLastScheduled()

Retrieves the instant in time just before this task was last executed by the background thread. A value of zero indicates that this task has never been executed.

Returns:long: the last time this task was executed or zero if never

getNextScheduled	back to summary
pack-priv synchronized long getNextScheduled() Retrieves the time at which this task is next scheduled for execution. Returns:long the time at which this task is next scheduled for execution

getNextScheduled

back to summary

pack-priv synchronized long getNextScheduled()

Retrieves the time at which this task is next scheduled for execution.

Returns:long: the time at which this task is next scheduled for execution

isCancelled	back to summary
pack-priv boolean isCancelled() Retrieves whether this task is cancelled. Returns:boolean true if cancelled, else false

isCancelled

back to summary

pack-priv boolean isCancelled()

Retrieves whether this task is cancelled.

Returns:boolean: true if cancelled, else false

setPeriod

back to summary

pack-priv synchronized Object setPeriod(final long newPeriod)

Sets the new periodicity of this task in milliseconds.

If this task is cancelled or the new period is identical to the current period, then this invocation has essentially no effect and this object is returned.

Otherwise, if the new period is greater than the current period, then a simple field assignment occurs and this object is returned.

If none of the previous cases hold, then this task is cancelled and a new, equivalent task with the new period is scheduled for immediate first execution and returned to the caller.

Parameters

newPeriod:long: the new period

Returns:Object

a task reference, as per the rules stated above.

updateSchedule

back to summary

pack-priv synchronized void updateSchedule(final long last, final long next)

Updates the last and next scheduled execution times.

Parameters

last:long: when this task was last executed
next:long: when this task is to be next executed

org.hsqldb.lib back to summary

protected Class HsqlTimer.TaskQueue

Class Inheritance

extends HsqlArrayHeap<HsqlTimer.Task>

java.lang.Object
org.hsqldb.lib.HsqlArrayHeap
org.hsqldb.lib.HsqlTimer.TaskQueue

Heap-based priority queue. Provides extensions to facilitate and simplify implementing timer functionality.

Field Summary

Inherited from org.hsqldb.lib.HsqlArrayHeap:: count heap oc

Constructor Summary

Access	Constructor and Description
pack-priv	TaskQueue(final int the initial capacity of the queue capacity, final Comparator<HsqlTimer.Task> The ObjectComparator this queue uses to maintain its Heap invariant. oc) Constructs a new TaskQueue with the specified initial capacity and ObjectComparator.

Method Summary

Modifier and Type	Method and Description
pack-priv void	addTask(final HsqlTimer.Task the task to add task) Type-safe add method.
pack-priv void	cancelAllTasks() Atomically removes all tasks in this queue and then and cancels them.
pack-priv synchronized void	park(final long the maximum time to wait in milliseconds. timeout) Causes the calling thread to wait until another thread invokes `unpark` or the specified amount of time has elapsed.
pack-priv synchronized HsqlTimer.Task	Returns: the earliest scheduled non-cancelled task, or null if no such task exists peekTask() Retrieves the head of this queue, without removing it.
pack-priv HsqlTimer.Task	Returns: this queue's head task or null if no such task exists removeTask() Type-safe remove method.
pack-priv synchronized void	signalTaskCancelled(HsqlTimer.Task a supposedly cancelled task task) Informs this queue that the given task is supposedly cancelled.
pack-priv synchronized void	unpark() Wakes up a single thread (if any) that is waiting on this queue's `park` method.

Inherited from org.hsqldb.lib.HsqlArrayHeap:: add clear isEmpty isFull peek remove size toString

Constructor Detail

TaskQueue

back to summary

pack-priv TaskQueue(final int capacity, final Comparator<HsqlTimer.Task> oc)

Constructs a new TaskQueue with the specified initial capacity and ObjectComparator.

Parameters

capacity:int: the initial capacity of the queue
oc:Comparator<HsqlTimer.Task>: The ObjectComparator this queue uses to maintain its Heap invariant.

Method Detail

addTask

back to summary

pack-priv void addTask(final HsqlTimer.Task task)

Type-safe add method.

Can be used to inject debugging or accounting behaviour.

Parameters

task:HsqlTimer.Task: the task to add

cancelAllTasks	back to summary
pack-priv void cancelAllTasks() Atomically removes all tasks in this queue and then and cancels them.

park back to summary

pack-priv synchronized void park(final long timeout) throws InterruptedException

Causes the calling thread to wait until another thread invokes unpark or the specified amount of time has elapsed. Implements the sync and wait(n) half of this queue's availability condition.

Parameters

timeout:long: the maximum time to wait in milliseconds.

Exceptions

InterruptedException:: if another thread has interrupted the current thread. The interrupted status of the current thread is cleared when this exception is thrown.

peekTask

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pack-priv synchronized HsqlTimer.Task peekTask()

Retrieves the head of this queue, without removing it.

This method has the side effect of removing tasks from the head of this queue until a non-cancelled task is encountered or this queue is empty.

If this queue is initially empty or is emptied in the process of finding the earliest scheduled non-cancelled task, then null is returned.

Returns:HsqlTimer.Task: the earliest scheduled non-cancelled task, or null if no such task exists

removeTask

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pack-priv HsqlTimer.Task removeTask()

Type-safe remove method.

Removes the head task from this queue.

Can be used to inject debugging or accounting behaviour.

Returns:HsqlTimer.Task: this queue's head task or null if no such task exists

signalTaskCancelled back to summary

pack-priv synchronized void signalTaskCancelled(HsqlTimer.Task task)

Informs this queue that the given task is supposedly cancelled.

If the indicated task is identical to the current head of this queue, then it is removed and this queue is unparked.

The cancelled status of the given task is not verified; it is assumed that the caller is well-behaved (always passes a non-null reference to a cancelled task).

Parameters

task:HsqlTimer.Task: a supposedly cancelled task

unpark	back to summary
pack-priv synchronized void unpark() Wakes up a single thread (if any) that is waiting on this queue's `park` method. Implements the sync and notify half of this queue's availability condition.

public final Class HsqlTimer

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protected Class HsqlTimer.Task

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protected Class HsqlTimer.TaskQueue

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protected Class HsqlTimer.TaskRunner

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