added in API level 26

Watchable

public interface Watchable

java.nio.file.Watchable


An object that may be registered with a watch service so that it can be watched for changes and events.

This interface defines the register method to register the object with a WatchService returning a WatchKey to represent the registration. An object may be registered with more than one watch service. Registration with a watch service is cancelled by invoking the key's cancel method.

Summary

Public methods

abstract WatchKey register(WatchService watcher, Kind[]<?> events, Modifier... modifiers)

Registers an object with a watch service.

abstract WatchKey register(WatchService watcher, Kind...<?> events)

Registers an object with a watch service.

Public methods

register

added in API level 26
public abstract WatchKey register (WatchService watcher, 
                Kind[]<?> events, 
                Modifier... modifiers)

Registers an object with a watch service.

If the file system object identified by this object is currently registered with the watch service then the watch key, representing that registration, is returned after changing the event set or modifiers to those specified by the events and modifiers parameters. Changing the event set does not cause pending events for the object to be discarded. Objects are automatically registered for the OVERFLOW event. This event is not required to be present in the array of events.

Otherwise the file system object has not yet been registered with the given watch service, so it is registered and the resulting new key is returned.

Implementations of this interface should specify the events they support.

Parameters
watcher WatchService: the watch service to which this object is to be registered

events Kind: the events for which this object should be registered

modifiers Modifier: the modifiers, if any, that modify how the object is registered

Returns
WatchKey a key representing the registration of this object with the given watch service

Throws
UnsupportedOperationException if unsupported events or modifiers are specified
IllegalArgumentException if an invalid of combination of events are modifiers are specified
ClosedWatchServiceException if the watch service is closed
IOException if an I/O error occurs
SecurityException if a security manager is installed and it denies an unspecified permission required to monitor this object. Implementations of this interface should specify the permission checks.

register

added in API level 26
public abstract WatchKey register (WatchService watcher, 
                Kind...<?> events)

Registers an object with a watch service.

An invocation of this method behaves in exactly the same way as the invocation

     watchable.register(watcher, events, new WatchEvent.Modifier[0]);
 

Parameters
watcher WatchService: the watch service to which this object is to be registered

events Kind: the events for which this object should be registered

Returns
WatchKey a key representing the registration of this object with the given watch service

Throws
UnsupportedOperationException if unsupported events are specified
IllegalArgumentException if an invalid of combination of events are specified
ClosedWatchServiceException if the watch service is closed
IOException if an I/O error occurs
SecurityException if a security manager is installed and it denies an unspecified permission required to monitor this object. Implementations of this interface should specify the permission checks.