decaf::util::Timer Class Reference

A facility for threads to schedule tasks for future execution in a background thread. More...

#include <src/main/decaf/util/Timer.h>

Public Member Functions
	Timer ()
	Timer (const std::string &name)
	Create a new Timer whose associated thread is assigned the name given.
virtual	~Timer ()
void	cancel ()
	Terminates this timer, discarding any currently scheduled tasks.
bool	awaitTermination (long long timeout, const decaf::util::concurrent::TimeUnit &unit)
	The caller will block until the Timer has completed termination meaning all tasks that where scheduled before cancelation have now completed and the executor is ready for deletion.
int	purge ()
	Removes all canceled tasks from this timer's task queue.
void	schedule (TimerTask *task, long long delay)
	Schedules the specified task for execution after the specified delay.
void	schedule (const decaf::lang::Pointer< TimerTask > &task, long long delay)
	Schedules the specified task for execution after the specified delay.
void	schedule (TimerTask *task, const Date &time)
	Schedules the specified task for execution at the specified time.
void	schedule (const decaf::lang::Pointer< TimerTask > &task, const Date &time)
	Schedules the specified task for execution at the specified time.
void	schedule (TimerTask *task, long long delay, long long period)
	Schedules the specified task for repeated fixed-delay execution, beginning after the specified delay.
void	schedule (const decaf::lang::Pointer< TimerTask > &task, long long delay, long long period)
	Schedules the specified task for repeated fixed-delay execution, beginning after the specified delay.
void	schedule (TimerTask *task, const Date &firstTime, long long period)
	Schedules the specified task for repeated fixed-delay execution, beginning at the specified time.
void	schedule (const decaf::lang::Pointer< TimerTask > &task, const Date &firstTime, long long period)
	Schedules the specified task for repeated fixed-delay execution, beginning at the specified time.
void	scheduleAtFixedRate (TimerTask *task, long long delay, long long period)
	Schedules the specified task for repeated fixed-rate execution, beginning after the specified delay.
void	scheduleAtFixedRate (const decaf::lang::Pointer< TimerTask > &task, long long delay, long long period)
	Schedules the specified task for repeated fixed-rate execution, beginning after the specified delay.
void	scheduleAtFixedRate (TimerTask *task, const Date &firstTime, long long period)
	Schedules the specified task for repeated fixed-rate execution, beginning at the specified time.
void	scheduleAtFixedRate (const decaf::lang::Pointer< TimerTask > &task, const Date &firstTime, long long period)
	Schedules the specified task for repeated fixed-rate execution, beginning at the specified time.

Detailed Description

A facility for threads to schedule tasks for future execution in a background thread.

Tasks may be scheduled for one-time execution, or for repeated execution at regular intervals.

Corresponding to each Timer object is a single background thread that is used to execute all of the timer's tasks, sequentially. Timer tasks should complete quickly. If a timer task takes excessive time to complete, it "hogs" the timer's task execution thread. This can, in turn, delay the execution of subsequent tasks, which may "bunch up" and execute in rapid succession when (and if) the offending task finally completes.

This class is thread-safe: multiple threads can share a single Timer object without the need for external synchronization.

This class does not offer real-time guarantees: it schedules tasks using the wait(long) method.

Since

1.0

Constructor & Destructor Documentation

decaf::util::Timer::Timer

(

)

decaf::util::Timer::Timer

(

const std::string &

name

)

Create a new Timer whose associated thread is assigned the name given.

Parameters

name	The name to assign to this Timer's Thread.

virtual decaf::util::Timer::~Timer ( )

virtual

Member Function Documentation

bool decaf::util::Timer::awaitTermination	(	long long	timeout,
		const decaf::util::concurrent::TimeUnit &	unit
	)

The caller will block until the Timer has completed termination meaning all tasks that where scheduled before cancelation have now completed and the executor is ready for deletion.

If the timeout period elapses before the Timer reaches the terminated state then this method return false to indicate it has not terminated.

Parameters

timeout	The amount of time to wait before abandoning the wait for termination.
unit	The unit of time that the timeout value represents.

Returns

true if the Timer terminated or false if the timeout expired.

Exceptions

InterruptedException

if this call is interrupted while awaiting termination.

void decaf::util::Timer::cancel

(

)

Terminates this timer, discarding any currently scheduled tasks.

Does not interfere with a currently executing task (if it exists). Once a timer has been terminated, its execution thread terminates gracefully, and no more tasks may be scheduled on it.

Note that calling this method from within the run method of a timer task that was invoked by this timer absolutely guarantees that the ongoing task execution is the last task execution that will ever be performed by this timer.

This method may be called repeatedly; the second and subsequent calls have no effect.

int decaf::util::Timer::purge

(

)

Removes all canceled tasks from this timer's task queue.

Calling this method has no effect on the behavior of the timer, but eliminates the canceled tasks from the queue causing the Timer to destroy the TimerTask pointer it was originally given, the caller should ensure that they no longer have any references to TimerTasks that were previously scheduled.

Most programs will have no need to call this method. It is designed for use by the rare application that cancels a large number of tasks. Calling this method trades time for space: the runtime of the method may be proportional to n + c log n, where n is the number of tasks in the queue and c is the number of canceled tasks.

This method can be called on a Timer object that has no scheduled tasks without error.

Returns

the number of tasks removed from the queue.

void decaf::util::Timer::schedule	(	TimerTask *	task,
		long long	delay
	)

Schedules the specified task for execution after the specified delay.

The TimerTask pointer is considered to be owned by the Timer class once it has been scheduled, the Timer will destroy its TimerTask's once they have been canceled or the Timer itself is canceled. A TimerTask is considered scheduled only when this method return without throwing an exception, until that time ownership is not considered to have been transferred to the Timer and the caller should ensure that the TimerTask gets deleted if an exception is thrown and no further attempts to schedule that TimerTask instance are planned.

Parameters

task	- task to be scheduled.
delay	- delay in milliseconds before task is to be executed.

Exceptions

NullPointerException	- if the TimerTask value is Null.
IllegalArgumentException	- if delay is negative, or delay + System.currentTimeMillis() is negative.
IllegalStateException	- if task was already scheduled or canceled, or timer was canceled.

void decaf::util::Timer::schedule	(	const decaf::lang::Pointer< TimerTask > &	task,
		long long	delay
	)

Schedules the specified task for execution after the specified delay.

Parameters

task	- task to be scheduled.
delay	- delay in milliseconds before task is to be executed.

Exceptions

NullPointerException	- if the TimerTask value is Null.
IllegalArgumentException	- if delay is negative, or delay + System.currentTimeMillis() is negative.
IllegalStateException	- if task was already scheduled or canceled, or timer was canceled.

void decaf::util::Timer::schedule	(	TimerTask *	task,
		const Date &	time
	)

Schedules the specified task for execution at the specified time.

If the time is in the past, the task is scheduled for immediate execution.

The TimerTask pointer is considered to be owned by the Timer class once it has been scheduled, the Timer will destroy its TimerTask's once they have been canceled or the Timer itself is canceled. A TimerTask is considered scheduled only when this method return without throwing an exception, until that time ownership is not considered to have been transferred to the Timer and the caller should ensure that the TimerTask gets deleted if an exception is thrown and no further attempts to schedule that TimerTask instance are planned.

Parameters

task	- task to be scheduled.
time	- time at which task is to be executed.

Exceptions

NullPointerException	- if the TimerTask value is Null.
IllegalArgumentException	- if time.getTime() is negative.
IllegalStateException	- if task was already scheduled or canceled, timer was canceled, or timer thread terminated.

void decaf::util::Timer::schedule	(	const decaf::lang::Pointer< TimerTask > &	task,
		const Date &	time
	)

Schedules the specified task for execution at the specified time.

If the time is in the past, the task is scheduled for immediate execution.

Parameters

task	- task to be scheduled.
time	- time at which task is to be executed.

Exceptions

NullPointerException	- if the TimerTask value is Null.
IllegalArgumentException	- if time.getTime() is negative.
IllegalStateException	- if task was already scheduled or canceled, timer was canceled, or timer thread terminated.

void decaf::util::Timer::schedule	(	TimerTask *	task,
		long long	delay,
		long long	period
	)

Schedules the specified task for repeated fixed-delay execution, beginning after the specified delay.

Subsequent executions take place at approximately regular intervals separated by the specified period.

The TimerTask pointer is considered to be owned by the Timer class once it has been scheduled, the Timer will destroy its TimerTask's once they have been canceled or the Timer itself is canceled. A TimerTask is considered scheduled only when this method return without throwing an exception, until that time ownership is not considered to have been transferred to the Timer and the caller should ensure that the TimerTask gets deleted if an exception is thrown and no further attempts to schedule that TimerTask instance are planned.

In fixed-delay execution, each execution is scheduled relative to the actual execution time of the previous execution. If an execution is delayed for any reason (such as other background activity), subsequent executions will be delayed as well. In the long run, the frequency of execution will generally be slightly lower than the reciprocal of the specified period (assuming the system clock underlying Object.wait(long long) is accurate).

Fixed-delay execution is appropriate for recurring activities that require "smoothness." In other words, it is appropriate for activities where it is more important to keep the frequency accurate in the short run than in the long run. This includes most animation tasks, such as blinking a cursor at regular intervals. It also includes tasks wherein regular activity is performed in response to human input, such as automatically repeating a character as long as a key is held down.

Parameters

task	- task to be scheduled.
delay	- delay in milliseconds before task is to be executed.
period	- time in milliseconds between successive task executions.

Exceptions

NullPointerException	- if the TimerTask value is Null.
IllegalArgumentException	- if delay is negative, or delay + System.currentTimeMillis() is negative.
IllegalStateException	- if task was already scheduled or canceled, timer was canceled, or timer thread terminated.

void decaf::util::Timer::schedule	(	const decaf::lang::Pointer< TimerTask > &	task,
		long long	delay,
		long long	period
	)

Schedules the specified task for repeated fixed-delay execution, beginning after the specified delay.

Subsequent executions take place at approximately regular intervals separated by the specified period.

In fixed-delay execution, each execution is scheduled relative to the actual execution time of the previous execution. If an execution is delayed for any reason (such as other background activity), subsequent executions will be delayed as well. In the long run, the frequency of execution will generally be slightly lower than the reciprocal of the specified period (assuming the system clock underlying Object.wait(long long) is accurate).

Fixed-delay execution is appropriate for recurring activities that require "smoothness." In other words, it is appropriate for activities where it is more important to keep the frequency accurate in the short run than in the long run. This includes most animation tasks, such as blinking a cursor at regular intervals. It also includes tasks wherein regular activity is performed in response to human input, such as automatically repeating a character as long as a key is held down.

Parameters

task	- task to be scheduled.
delay	- delay in milliseconds before task is to be executed.
period	- time in milliseconds between successive task executions.

Exceptions

NullPointerException	- if the TimerTask value is Null.
IllegalArgumentException	- if delay is negative, or delay + System.currentTimeMillis() is negative.
IllegalStateException	- if task was already scheduled or canceled, timer was canceled, or timer thread terminated.

void decaf::util::Timer::schedule	(	TimerTask *	task,
		const Date &	firstTime,
		long long	period
	)

Schedules the specified task for repeated fixed-delay execution, beginning at the specified time.

Subsequent executions take place at approximately regular intervals separated by the specified period.

The TimerTask pointer is considered to be owned by the Timer class once it has been scheduled, the Timer will destroy its TimerTask's once they have been canceled or the Timer itself is canceled. A TimerTask is considered scheduled only when this method return without throwing an exception, until that time ownership is not considered to have been transferred to the Timer and the caller should ensure that the TimerTask gets deleted if an exception is thrown and no further attempts to schedule that TimerTask instance are planned.

In fixed-delay execution, each execution is scheduled relative to the actual execution time of the previous execution. If an execution is delayed for any reason (such as other background activity), subsequent executions will be delayed as well. In the long run, the frequency of execution will generally be slightly lower than the reciprocal of the specified period (assuming the system clock underlying Object.wait(long long) is accurate).

Fixed-delay execution is appropriate for recurring activities that require "smoothness." In other words, it is appropriate for activities where it is more important to keep the frequency accurate in the short run than in the long run. This includes most animation tasks, such as blinking a cursor at regular intervals. It also includes tasks wherein regular activity is performed in response to human input, such as automatically repeating a character as long as a key is held down.

Parameters

task	- task to be scheduled.
firstTime	- First time at which task is to be executed.
period	- time in milliseconds between successive task executions.

Exceptions

NullPointerException	- if the TimerTask value is Null.
IllegalArgumentException	- if time.getTime() is negative.
IllegalStateException	- if task was already scheduled or canceled, timer was canceled, or timer thread terminated.

void decaf::util::Timer::schedule	(	const decaf::lang::Pointer< TimerTask > &	task,
		const Date &	firstTime,
		long long	period
	)

Schedules the specified task for repeated fixed-delay execution, beginning at the specified time.

Subsequent executions take place at approximately regular intervals separated by the specified period.

In fixed-delay execution, each execution is scheduled relative to the actual execution time of the previous execution. If an execution is delayed for any reason (such as other background activity), subsequent executions will be delayed as well. In the long run, the frequency of execution will generally be slightly lower than the reciprocal of the specified period (assuming the system clock underlying Object.wait(long long) is accurate).

Fixed-delay execution is appropriate for recurring activities that require "smoothness." In other words, it is appropriate for activities where it is more important to keep the frequency accurate in the short run than in the long run. This includes most animation tasks, such as blinking a cursor at regular intervals. It also includes tasks wherein regular activity is performed in response to human input, such as automatically repeating a character as long as a key is held down.

Parameters

task	- task to be scheduled.
firstTime	- First time at which task is to be executed.
period	- time in milliseconds between successive task executions.

Exceptions

NullPointerException	- if the TimerTask value is Null.
IllegalArgumentException	- if time.getTime() is negative.
IllegalStateException	- if task was already scheduled or canceled, timer was canceled, or timer thread terminated.

void decaf::util::Timer::scheduleAtFixedRate	(	TimerTask *	task,
		long long	delay,
		long long	period
	)

Schedules the specified task for repeated fixed-rate execution, beginning after the specified delay.

Subsequent executions take place at approximately regular intervals, separated by the specified period.

The TimerTask pointer is considered to be owned by the Timer class once it has been scheduled, the Timer will destroy its TimerTask's once they have been canceled or the Timer itself is canceled. A TimerTask is considered scheduled only when this method return without throwing an exception, until that time ownership is not considered to have been transferred to the Timer and the caller should ensure that the TimerTask gets deleted if an exception is thrown and no further attempts to schedule that TimerTask instance are planned.

In fixed-rate execution, each execution is scheduled relative to the scheduled execution time of the initial execution. If an execution is delayed for any reason (such as garbage collection or other background activity), two or more executions will occur in rapid succession to "catch up." In the long run, the frequency of execution will be exactly the reciprocal of the specified period (assuming the system clock underlying Object.wait(long) is accurate).

Fixed-rate execution is appropriate for recurring activities that are sensitive to absolute time, such as ringing a chime every hour on the hour, or running scheduled maintenance every day at a particular time. It is also appropriate for recurring activities where the total time to perform a fixed number of executions is important, such as a count down timer that ticks once every second for ten seconds. Finally, fixed-rate execution is appropriate for scheduling multiple repeating timer tasks that must remain synchronized with respect to one another.

Parameters

task	- task to be scheduled.
delay	- delay in milliseconds before task is to be executed.
period	- time in milliseconds between successive task executions.

Exceptions

NullPointerException	- if the TimerTask value is Null.
IllegalArgumentException	- if delay is negative, or delay + System.currentTimeMillis() is negative.
IllegalStateException	- if task was already scheduled or canceled, timer was canceled, or timer thread terminated.

void decaf::util::Timer::scheduleAtFixedRate	(	const decaf::lang::Pointer< TimerTask > &	task,
		long long	delay,
		long long	period
	)

Schedules the specified task for repeated fixed-rate execution, beginning after the specified delay.

Subsequent executions take place at approximately regular intervals, separated by the specified period.

In fixed-rate execution, each execution is scheduled relative to the scheduled execution time of the initial execution. If an execution is delayed for any reason (such as garbage collection or other background activity), two or more executions will occur in rapid succession to "catch up." In the long run, the frequency of execution will be exactly the reciprocal of the specified period (assuming the system clock underlying Object.wait(long) is accurate).

Fixed-rate execution is appropriate for recurring activities that are sensitive to absolute time, such as ringing a chime every hour on the hour, or running scheduled maintenance every day at a particular time. It is also appropriate for recurring activities where the total time to perform a fixed number of executions is important, such as a countdown timer that ticks once every second for ten seconds. Finally, fixed-rate execution is appropriate for scheduling multiple repeating timer tasks that must remain synchronized with respect to one another.

Parameters

task	- task to be scheduled.
delay	- delay in milliseconds before task is to be executed.
period	- time in milliseconds between successive task executions.

Exceptions

NullPointerException	- if the TimerTask value is Null.
IllegalArgumentException	- if delay is negative, or delay + System.currentTimeMillis() is negative.
IllegalStateException	- if task was already scheduled or canceled, timer was canceled, or timer thread terminated.

void decaf::util::Timer::scheduleAtFixedRate	(	TimerTask *	task,
		const Date &	firstTime,
		long long	period
	)

Schedules the specified task for repeated fixed-rate execution, beginning at the specified time.

Subsequent executions take place at approximately regular intervals, separated by the specified period.

The TimerTask pointer is considered to be owned by the Timer class once it has been scheduled, the Timer will destroy its TimerTask's once they have been canceled or the Timer itself is canceled. A TimerTask is considered scheduled only when this method return without throwing an exception, until that time ownership is not considered to have been transferred to the Timer and the caller should ensure that the TimerTask gets deleted if an exception is thrown and no further attempts to schedule that TimerTask instance are planned.

In fixed-rate execution, each execution is scheduled relative to the scheduled execution time of the initial execution. If an execution is delayed for any reason (such as garbage collection or other background activity), two or more executions will occur in rapid succession to "catch up." In the long run, the frequency of execution will be exactly the reciprocal of the specified period (assuming the system clock underlying Object.wait(long) is accurate).

Fixed-rate execution is appropriate for recurring activities that are sensitive to absolute time, such as ringing a chime every hour on the hour, or running scheduled maintenance every day at a particular time. It is also appropriate for recurring activities where the total time to perform a fixed number of executions is important, such as a countdown timer that ticks once every second for ten seconds. Finally, fixed-rate execution is appropriate for scheduling multiple repeating timer tasks that must remain synchronized with respect to one another.

Parameters

task	- task to be scheduled.
firstTime	- First time at which task is to be executed.
period	- time in milliseconds between successive task executions.

Exceptions

NullPointerException	- if the TimerTask value is Null.
IllegalArgumentException	- if time.getTime() is negative.
IllegalStateException	- if task was already scheduled or canceled, timer was canceled, or timer thread terminated.

void decaf::util::Timer::scheduleAtFixedRate	(	const decaf::lang::Pointer< TimerTask > &	task,
		const Date &	firstTime,
		long long	period
	)

Schedules the specified task for repeated fixed-rate execution, beginning at the specified time.

Subsequent executions take place at approximately regular intervals, separated by the specified period.

In fixed-rate execution, each execution is scheduled relative to the scheduled execution time of the initial execution. If an execution is delayed for any reason (such as garbage collection or other background activity), two or more executions will occur in rapid succession to "catch up." In the long run, the frequency of execution will be exactly the reciprocal of the specified period (assuming the system clock underlying Object.wait(long) is accurate).

Fixed-rate execution is appropriate for recurring activities that are sensitive to absolute time, such as ringing a chime every hour on the hour, or running scheduled maintenance every day at a particular time. It is also appropriate for recurring activities where the total time to perform a fixed number of executions is important, such as a countdown timer that ticks once every second for ten seconds. Finally, fixed-rate execution is appropriate for scheduling multiple repeating timer tasks that must remain synchronized with respect to one another.

Parameters

task	- task to be scheduled.
firstTime	- First time at which task is to be executed.
period	- time in milliseconds between successive task executions.

Exceptions

NullPointerException	- if the TimerTask value is Null.
IllegalArgumentException	- if time.getTime() is negative.
IllegalStateException	- if task was already scheduled or canceled, timer was canceled, or timer thread terminated.

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The documentation for this class was generated from the following file:

• src/main/decaf/util/Timer.h