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package java.nio.file;

import java.io.IOException;


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. 
See Also:
Since:1.7
/**
 * An object that may be registered with a watch service so that it can be
 * <em>watched</em> for changes and events.
 *
 * <p> This interface defines the {@link #register register} method to register
 * the object with a {@link WatchService} returning a {@link 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 {@link WatchKey#cancel cancel} method.
 *
 * @since 1.7
 *
 * @see Path#register
 */

public interface Watchable {

    
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.

Params:
  • watcher – 
         the watch service to which this object is to be registered
  • events – 
         the events for which this object should be registered
  • modifiers – 
         the modifiers, if any, that modify how the object is registered
Throws:
Returns: a key representing the registration of this object with the
         given watch service
/**
     * Registers an object with a watch service.
     *
     * <p> 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 {@code events} and {@code modifiers} parameters.
     * Changing the event set does not cause pending events for the object to be
     * discarded. Objects are automatically registered for the {@link
     * StandardWatchEventKinds#OVERFLOW OVERFLOW} event. This event is not
     * required to be present in the array of events.
     *
     * <p> 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.
     *
     * <p> Implementations of this interface should specify the events they
     * support.
     *
     * @param   watcher
     *          the watch service to which this object is to be registered
     * @param   events
     *          the events for which this object should be registered
     * @param   modifiers
     *          the modifiers, if any, that modify how the object is registered
     *
     * @return  a key representing the registration of this object with the
     *          given watch service
     *
     * @throws  UnsupportedOperationException
     *          if unsupported events or modifiers are specified
     * @throws  IllegalArgumentException
     *          if an invalid of combination of events are modifiers are specified
     * @throws  ClosedWatchServiceException
     *          if the watch service is closed
     * @throws  IOException
     *          if an I/O error occurs
     * @throws  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.
     */
    WatchKey register(WatchService watcher,
                      WatchEvent.Kind<?>[] events,
                      WatchEvent.Modifier... modifiers)
        throws IOException;


    
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]); 


Params:
  • watcher – 
         the watch service to which this object is to be registered
  • events – 
         the events for which this object should be registered
Throws:
Returns: a key representing the registration of this object with the
         given watch service
/**
     * Registers an object with a watch service.
     *
     * <p> An invocation of this method behaves in exactly the same way as the
     * invocation
     * <pre>
     *     watchable.{@link #register(WatchService,WatchEvent.Kind[],WatchEvent.Modifier[]) register}(watcher, events, new WatchEvent.Modifier[0]);
     * </pre>
     *
     * @param   watcher
     *          the watch service to which this object is to be registered
     * @param   events
     *          the events for which this object should be registered
     *
     * @return  a key representing the registration of this object with the
     *          given watch service
     *
     * @throws  UnsupportedOperationException
     *          if unsupported events are specified
     * @throws  IllegalArgumentException
     *          if an invalid of combination of events are specified
     * @throws  ClosedWatchServiceException
     *          if the watch service is closed
     * @throws  IOException
     *          if an I/O error occurs
     * @throws  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.
     */
    WatchKey register(WatchService watcher, WatchEvent.Kind<?>... events)
        throws IOException;
}