name.pachler.nio.file

Class WatchKey

java.lang.Object

name.pachler.nio.file.WatchKey

Direct Known Subclasses:

PathWatchKey

public abstract class WatchKey
extends java.lang.Object

A WatchKey represents a Watchable's registration for events with a WatchService. It is created on registration and subsequently used to retreive WatchEvents.
To stop receiving events from a WatchService (that is, undoing registration), use the cancel() method. Note that this will invalidate the WatchKey, which should then be discarded (as it cannot be reused).

See Also:

WatchService.poll(), WatchService.take(), pollEvents()

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	WatchKey()

Method Summary

Modifier and Type	Method and Description
abstract void	cancel() This cancels the registration with the WatchService that this WatchKey was registered with.
abstract boolean	isValid()
abstract java.util.List<WatchEvent<?>>	pollEvents() Returns the events that have occurred for this WatchKey.
abstract boolean	reset() Resets this WatchKey (marks it as non-signalled) so that it's corresponding WatchService can report it again via it's WatchService.poll() and WatchService.take() methods.

Methods inherited from class java.lang.Object

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

Constructor Detail

WatchKey

protected WatchKey()

Method Detail

cancel

public abstract void cancel()

This cancels the registration with the WatchService that this WatchKey was registered with. This means that no new events will be delivered to this key any more. Events that are pending can still be retreived with pollEvents(), and if the WatchKey is still marked as signalled a call to WatchService's poll() or take() functions will still return it.

isValid

public abstract boolean isValid()

Returns:

if this watch key is valid. A watch key is valid if

• It has not been canceled
• The WatchService is not yet closed

pollEvents

public abstract java.util.List<WatchEvent<?>> pollEvents()

Returns the events that have occurred for this WatchKey. Just calling this method will not reset the signalled state of this key; you'll have to call #reset() to indicate to the WatchService that the the client is ready to receive more events and that the key can be re-queued. After the WatchService has determined that events have occurred for a registered Watchable represented by a given WatchKey, it will return that key when the client calls it's WatchService#take() or WatchService#poll() methods.

Returns:

a list of events that have occurred since the last time that #pollEvents() was called.

reset

public abstract boolean reset()

Resets this WatchKey (marks it as non-signalled) so that it's corresponding WatchService can report it again via it's WatchService.poll() and WatchService.take() methods.

Returns:

true if the key could be reset, false otherwise (typically if the corresponding WatchService has been closed or if the the key was not signalled).