com.iparelan.util
Class PeriodicSuspendableThread

java.lang.Object
  java.lang.Thread
      com.iparelan.util.PeriodicSuspendableThread

All Implemented Interfaces:

SuspendableTask, Runnable

@Copyright(value="Copyright © 2008, Iparelan Solutions, LLC. All rights reserved.")
public final class PeriodicSuspendableThread
extends Thread
implements SuspendableTask

A periodic background (daemon) task that can be suspended.

Version:

July 2008

Author:

Greg Mattes

Nested Class Summary

Nested classes/interfaces inherited from class java.lang.Thread

Thread.State, Thread.UncaughtExceptionHandler

Field Summary

static int	DEFAULT_REFRESH_PERIOD
private static String	DEFAULT_THREAD_NAME_PREFIX
private Condition	disabledCondition
private boolean	enabled Decides whether this Thread is suspended/disabled or enabled.
private Condition	enabledCondition
private Runnable	errorHook
private Lock	lock
(package private) static Logger	LOGGER
static String	LOGGER_NAME
private static int	MILLISECONDS_PER_SECOND
private int	refreshPeriodMillis
private static AtomicLong	serialNumberGenerator
private Runnable	work

Fields inherited from class java.lang.Thread

MAX_PRIORITY, MIN_PRIORITY, NORM_PRIORITY

Constructor Summary

PeriodicSuspendableThread(Runnable work)
Creates a PeriodicSuspendableThreadImpl with a default name and a default refresh period (5 seconds).

PeriodicSuspendableThread(String name, int refreshPeriod, Runnable work, Runnable errorHook)
Creates a PeriodicSuspendableThreadImpl.

Method Summary

void	disable() "Turns-off" this task.
void	enable() "Turns-on" this task.
private void	ensureEnableCalled() Barrier that waits until this thread is "turned-on."
boolean	isEnabled() Tells whether this task is enabled.
void	run() Repeatedly performs the work of the thread at periodic intervals.

Methods inherited from class java.lang.Thread

activeCount, checkAccess, countStackFrames, currentThread, destroy, dumpStack, enumerate, getAllStackTraces, getContextClassLoader, getDefaultUncaughtExceptionHandler, getId, getName, getPriority, getStackTrace, getState, getThreadGroup, getUncaughtExceptionHandler, holdsLock, interrupt, interrupted, isAlive, isDaemon, isInterrupted, join, join, join, resume, setContextClassLoader, setDaemon, setDefaultUncaughtExceptionHandler, setName, setPriority, setUncaughtExceptionHandler, sleep, sleep, start, stop, stop, suspend, toString, yield

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

LOGGER_NAME

public static final String LOGGER_NAME

See Also:

Constant Field Values

LOGGER

static final Logger LOGGER

DEFAULT_REFRESH_PERIOD

public static final int DEFAULT_REFRESH_PERIOD

See Also:

Constant Field Values

MILLISECONDS_PER_SECOND

private static final int MILLISECONDS_PER_SECOND

See Also:

Constant Field Values

serialNumberGenerator

private static final AtomicLong serialNumberGenerator

DEFAULT_THREAD_NAME_PREFIX

private static final String DEFAULT_THREAD_NAME_PREFIX

See Also:

Constant Field Values

lock

private final Lock lock

enabledCondition

private final Condition enabledCondition

disabledCondition

private final Condition disabledCondition

work

private final Runnable work

errorHook

private final Runnable errorHook

refreshPeriodMillis

private final int refreshPeriodMillis

enabled

private boolean enabled

Decides whether this Thread is suspended/disabled or enabled.

Constructor Detail

PeriodicSuspendableThread

public PeriodicSuspendableThread(Runnable work)

Creates a PeriodicSuspendableThreadImpl with a default name and a default refresh period (5 seconds).

Parameters:

work - The Runnable that specifies the work performed by this PeriodicSuspendableThread. May not be null.

Throws:

IllegalArgumentException - Iff work is null.

PeriodicSuspendableThread

public PeriodicSuspendableThread(String name,
                                 int refreshPeriod,
                                 Runnable work,
                                 @Nullable
                                 Runnable errorHook)

Creates a PeriodicSuspendableThreadImpl.

Parameters:

name - The Thread name, this parameter has the same semantics and restrictions as that of Thread.Thread(String).

refreshPeriod - The refresh period in seconds.

work - The Runnable that specifies the work performed by this PeriodicSuspendableThread. May not be null.

errorHook - The Runnable that specifies the policy to invoke if work terminates abruptly by throwing an exception or raising an error other than InterruptedException. In the case InterruptedException, the current execution of work is stopped, but future executions are attempted. Any exceptions or errors thrown by errorHook are ignored. May be null.

Throws:

IllegalArgumentException - Iff work is null.

Method Detail

isEnabled

public boolean isEnabled()

Description copied from interface: SuspendableTask

Tells whether this task is enabled.

Specified by:

isEnabled in interface SuspendableTask

Returns:

true if this task is enabled, otherwise false.

enable

public void enable()

Description copied from interface: SuspendableTask

"Turns-on" this task. Calling this method is not guaranteed to commence task execution. Calling SuspendableTask.disable() before task execution begins may stop task execution.

Specified by:

enable in interface SuspendableTask

disable

public void disable()

Description copied from interface: SuspendableTask

"Turns-off" this task.

The task may not be turned off immediately if it does not respond to the thread interruption scheme, or if it is not blocked.

Specified by:

disable in interface SuspendableTask

ensureEnableCalled

private void ensureEnableCalled()

Barrier that waits until this thread is "turned-on."

See Also:

enable()

run

public void run()

Repeatedly performs the work of the thread at periodic intervals. A pause is taken after each iteration of work. The thread must be enabled for work to be performed.

Either the work or the pause may be interrupted. In such cases the next pause or work iteration is performed, respectively. The work can be interrupted if the code invoked by work.run() satisfies the conditions described by Thread.interrupt(). If none of these conditions hold, then the current work iteration cannot be interrupted, in particular, the deprecated Thread.suspend() is not invoked.

The pause duration is constant, save for interruption, in particular, it is not affected by the work duration.

Specified by:

run in interface Runnable

Overrides:

run in class Thread