java.nio.channels
Class Selector

java.lang.Object
  java.nio.channels.Selector

Direct Known Subclasses:

AbstractSelector

public abstract class Selector
extends Object

A controller for selection of SelectableChannel objects. Selectable channels can be registered with a selector, and get SelectionKey as a linkage. The keys are also added to the selector's keyset. The SelectionKey can be cancelled so that the corresponding channel is no longer registered with the selector. By invoking the select operation, the keyset is checked and all keys that are cancelled since last select operation are moved to cancelledKey set. During the select operation, the channels registered with this selector are checked to see whether they are ready for operation according to their interesting operation.

Constructor Summary

protected

Selector() The constructor.

Method Summary

abstract void	close() Closes this selector.
abstract boolean	isOpen() Tells whether this selector is open.
abstract Set<SelectionKey>	keys() Gets the set of registered keys.
static Selector	open() The factory method for selector.
abstract SelectorProvider	provider() Gets the provider of this selector.
abstract int	select() Detects if any of the registered channels are ready for I/O operations according to their interesting operation.
abstract int	select(long timeout) Detects if any of the registered channels are ready for I/O operations according to their interesting operation.This operation will not return until some of the channels are ready or wakeup is invoked or timeout expired.
abstract Set<SelectionKey>	selectedKeys() Gets the keys whose channels are ready for operation.
abstract int	selectNow() Detects if any of the registered channels are ready for I/O operations according to their interesting operation.This operation will not return immediately.
abstract Selector	wakeup() Forces the blocked select operation to return immediately.

Methods inherited from class java.lang.Object

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

Constructor Detail

Selector

protected Selector()

The constructor.

Method Detail

open

public static Selector open()
                     throws IOException

The factory method for selector.

Returns:

a new selector

Throws:

IOException - if I/O error occurs

close

public abstract void close()
                    throws IOException

Closes this selector.

Throws:

IOException - if I/O error occurs

isOpen

public abstract boolean isOpen()

Tells whether this selector is open.

Returns:

true if this selector is not closed

keys

public abstract Set<SelectionKey> keys()

Gets the set of registered keys.

Returns:

the keyset of registered keys

provider

public abstract SelectorProvider provider()

Gets the provider of this selector.

Returns:

the provider of this selector

select

public abstract int select()
                    throws IOException

Detects if any of the registered channels are ready for I/O operations according to their interesting operation. This operation will not return until some of the channels are ready or wakeup is invoked.

Returns:

the number of channels that are ready for operation

Throws:

IOException - if I/O error occurs

ClosedSelectorException - If the selector is closed

select

public abstract int select(long timeout)
                    throws IOException

Detects if any of the registered channels are ready for I/O operations according to their interesting operation.This operation will not return until some of the channels are ready or wakeup is invoked or timeout expired.

Parameters:

timeout - the timeout in millisecond

Returns:

the number of channels that are ready for operation

Throws:

IOException - if I/O error occurs

ClosedSelectorException - If the selector is closed

IllegalArgumentException - If the given timeout argument is less than zero

selectedKeys

public abstract Set<SelectionKey> selectedKeys()

Gets the keys whose channels are ready for operation.

Returns:

the keys whose channels are ready for operation

selectNow

public abstract int selectNow()
                       throws IOException

Detects if any of the registered channels are ready for I/O operations according to their interesting operation.This operation will not return immediately.

Returns:

the number of channels that are ready for operation

Throws:

IOException - if I/O error occur

ClosedSelectorException - If the selector is closed

wakeup

public abstract Selector wakeup()

Forces the blocked select operation to return immediately. If no select operation is blocked currently, the next select operation shall return immediately.

Returns:

this selector

Throws:

ClosedSelectorException - If the selector is closed