Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) Summary: [Protected Ctors](https://developer.android.com/reference/java/nio/channels/SelectableChannel#proctors) \| [Methods](https://developer.android.com/reference/java/nio/channels/SelectableChannel#pubmethods) \| [Inherited Methods](https://developer.android.com/reference/java/nio/channels/SelectableChannel#inhmethods)
# SelectableChannel
`
public
abstract
class
SelectableChannel
`
`
`
`
extends https://developer.android.com/reference/java/nio/channels/spi/AbstractInterruptibleChannel
`
`
implements
https://developer.android.com/reference/java/nio/channels/Channel
`
|---|---|---|
| [java.lang.Object](https://developer.android.com/reference/java/lang/Object) |||
| ↳ | [java.nio.channels.spi.AbstractInterruptibleChannel](https://developer.android.com/reference/java/nio/channels/spi/AbstractInterruptibleChannel) ||
| | ↳ | java.nio.channels.SelectableChannel |
|---|
| Known direct subclasses [AbstractSelectableChannel](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelectableChannel) |---|---| | [AbstractSelectableChannel](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelectableChannel) | Base implementation class for selectable channels. | |
|---|
| Known indirect subclasses [DatagramChannel](https://developer.android.com/reference/java/nio/channels/DatagramChannel), [Pipe.SinkChannel](https://developer.android.com/reference/java/nio/channels/Pipe.SinkChannel), [Pipe.SourceChannel](https://developer.android.com/reference/java/nio/channels/Pipe.SourceChannel), [ServerSocketChannel](https://developer.android.com/reference/java/nio/channels/ServerSocketChannel), [SocketChannel](https://developer.android.com/reference/java/nio/channels/SocketChannel) |---|---| | [DatagramChannel](https://developer.android.com/reference/java/nio/channels/DatagramChannel) | A selectable channel for datagram-oriented sockets. | | [Pipe.SinkChannel](https://developer.android.com/reference/java/nio/channels/Pipe.SinkChannel) | A channel representing the writable end of a `https://developer.android.com/reference/java/nio/channels/Pipe`. | | [Pipe.SourceChannel](https://developer.android.com/reference/java/nio/channels/Pipe.SourceChannel) | A channel representing the readable end of a `https://developer.android.com/reference/java/nio/channels/Pipe`. | | [ServerSocketChannel](https://developer.android.com/reference/java/nio/channels/ServerSocketChannel) | A selectable channel for stream-oriented listening sockets. | | [SocketChannel](https://developer.android.com/reference/java/nio/channels/SocketChannel) | A selectable channel for stream-oriented connecting sockets. | |
*** ** * ** ***
A channel that can be multiplexed via a `https://developer.android.com/reference/java/nio/channels/Selector`.
In order to be used with a selector, an instance of this class must
first be *registered* via the `https://developer.android.com/reference/java/nio/channels/SelectableChannel#register(java.nio.channels.Selector,%20int,%20java.lang.Object)` method. This method returns a new `https://developer.android.com/reference/java/nio/channels/SelectionKey` object
that represents the channel's registration with the selector.
Once registered with a selector, a channel remains registered until it
is *deregistered*. This involves deallocating whatever resources were
allocated to the channel by the selector.
A channel cannot be deregistered directly; instead, the key representing
its registration must be *cancelled*. Cancelling a key requests that
the channel be deregistered during the selector's next selection operation.
A key may be cancelled explicitly by invoking its `https://developer.android.com/reference/java/nio/channels/SelectionKey#cancel()` method. All of a channel's keys are cancelled
implicitly when the channel is closed, whether by invoking its `https://developer.android.com/reference/java/nio/channels/Channel#close()` method or by interrupting a thread blocked in an I/O
operation upon the channel.
If the selector itself is closed then the channel will be deregistered,
and the key representing its registration will be invalidated, without
further delay.
A channel may be registered at most once with any particular selector.
Whether or not a channel is registered with one or more selectors may be
determined by invoking the `https://developer.android.com/reference/java/nio/channels/SelectableChannel#isRegistered()` method.
Selectable channels are safe for use by multiple concurrent
threads.
## Blocking mode
A selectable channel is either in *blocking* mode or in *non-blocking* mode. In blocking mode, every I/O operation invoked upon the channel will block until it completes. In non-blocking mode an I/O operation will never block and may transfer fewer bytes than were requested or possibly no bytes at all. The blocking mode of a selectable channel may be determined by invoking its `https://developer.android.com/reference/java/nio/channels/SelectableChannel#isBlocking()` method.
Newly-created selectable channels are always in blocking mode.
Non-blocking mode is most useful in conjunction with selector-based
multiplexing. A channel must be placed into non-blocking mode before being
registered with a selector, and may not be returned to blocking mode until
it has been deregistered.
**See also:**
- `https://developer.android.com/reference/java/nio/channels/SelectionKey`
- `https://developer.android.com/reference/java/nio/channels/Selector`
## Summary
| ### Protected constructors ||
|---|---|
| ` https://developer.android.com/reference/java/nio/channels/SelectableChannel#SelectableChannel()() ` Initializes a new instance of this class. |
| ### Public methods ||
|---|---|
| ` abstract https://developer.android.com/reference/java/lang/Object` | ` https://developer.android.com/reference/java/nio/channels/SelectableChannel#blockingLock()() ` Retrieves the object upon which the `https://developer.android.com/reference/java/nio/channels/SelectableChannel#configureBlocking(boolean)` and `https://developer.android.com/reference/java/nio/channels/SelectableChannel#register(java.nio.channels.Selector,%20int)` methods synchronize. |
| ` abstract https://developer.android.com/reference/java/nio/channels/SelectableChannel` | ` https://developer.android.com/reference/java/nio/channels/SelectableChannel#configureBlocking(boolean)(boolean block) ` Adjusts this channel's blocking mode. |
| ` abstract boolean` | ` https://developer.android.com/reference/java/nio/channels/SelectableChannel#isBlocking()() ` Tells whether or not every I/O operation on this channel will block until it completes. |
| ` abstract boolean` | ` https://developer.android.com/reference/java/nio/channels/SelectableChannel#isRegistered()() ` Tells whether or not this channel is currently registered with any selectors. |
| ` abstract https://developer.android.com/reference/java/nio/channels/SelectionKey` | ` https://developer.android.com/reference/java/nio/channels/SelectableChannel#keyFor(java.nio.channels.Selector)(https://developer.android.com/reference/java/nio/channels/Selector sel) ` Retrieves the key representing the channel's registration with the given selector. |
| ` abstract https://developer.android.com/reference/java/nio/channels/spi/SelectorProvider` | ` https://developer.android.com/reference/java/nio/channels/SelectableChannel#provider()() ` Returns the provider that created this channel. |
| ` abstract https://developer.android.com/reference/java/nio/channels/SelectionKey` | ` https://developer.android.com/reference/java/nio/channels/SelectableChannel#register(java.nio.channels.Selector,%20int,%20java.lang.Object)(https://developer.android.com/reference/java/nio/channels/Selector sel, int ops, https://developer.android.com/reference/java/lang/Object att) ` Registers this channel with the given selector, returning a selection key. |
| ` final https://developer.android.com/reference/java/nio/channels/SelectionKey` | ` https://developer.android.com/reference/java/nio/channels/SelectableChannel#register(java.nio.channels.Selector,%20int)(https://developer.android.com/reference/java/nio/channels/Selector sel, int ops) ` Registers this channel with the given selector, returning a selection key. |
| ` abstract int` | ` https://developer.android.com/reference/java/nio/channels/SelectableChannel#validOps()() ` Returns an [operation set](https://developer.android.com/reference/java/nio/channels/SelectionKey#opsets) identifying this channel's supported operations. |
| ### Inherited methods |
|---|---|
| From class ` https://developer.android.com/reference/java/nio/channels/spi/AbstractInterruptibleChannel ` |---|---| | ` final void` | ` https://developer.android.com/reference/java/nio/channels/spi/AbstractInterruptibleChannel#begin()() ` Marks the beginning of an I/O operation that might block indefinitely. | | ` final void` | ` https://developer.android.com/reference/java/nio/channels/spi/AbstractInterruptibleChannel#close()() ` Closes this channel. | | ` final void` | ` https://developer.android.com/reference/java/nio/channels/spi/AbstractInterruptibleChannel#end(boolean)(boolean completed) ` Marks the end of an I/O operation that might block indefinitely. | | ` abstract void` | ` https://developer.android.com/reference/java/nio/channels/spi/AbstractInterruptibleChannel#implCloseChannel()() ` Closes this channel. | | ` final boolean` | ` https://developer.android.com/reference/java/nio/channels/spi/AbstractInterruptibleChannel#isOpen()() ` Tells whether or not this channel is open. | ||
| From class ` https://developer.android.com/reference/java/lang/Object ` |---|---| | ` https://developer.android.com/reference/java/lang/Object` | ` https://developer.android.com/reference/java/lang/Object#clone()() ` Creates and returns a copy of this object. | | ` boolean` | ` https://developer.android.com/reference/java/lang/Object#equals(java.lang.Object)(https://developer.android.com/reference/java/lang/Object obj) ` Indicates whether some other object is "equal to" this one. | | ` void` | ` https://developer.android.com/reference/java/lang/Object#finalize()() ` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. | | ` final https://developer.android.com/reference/java/lang/Class` | ` https://developer.android.com/reference/java/lang/Object#getClass()() ` Returns the runtime class of this `Object`. | | ` int` | ` https://developer.android.com/reference/java/lang/Object#hashCode()() ` Returns a hash code value for the object. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#notify()() ` Wakes up a single thread that is waiting on this object's monitor. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#notifyAll()() ` Wakes up all threads that are waiting on this object's monitor. | | ` https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/lang/Object#toString()() ` Returns a string representation of the object. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait(long,%20int)(long timeoutMillis, int nanos) ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait(long)(long timeoutMillis) ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait()() ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*. | ||
| From interface ` https://developer.android.com/reference/java/nio/channels/Channel ` |---|---| | ` abstract void` | ` https://developer.android.com/reference/java/nio/channels/Channel#close()() ` Closes this channel. | | ` abstract boolean` | ` https://developer.android.com/reference/java/nio/channels/Channel#isOpen()() ` Tells whether or not this channel is open. | ||
| From interface ` https://developer.android.com/reference/java/nio/channels/InterruptibleChannel ` |---|---| | ` abstract void` | ` https://developer.android.com/reference/java/nio/channels/InterruptibleChannel#close()() ` Closes this channel. | ||
| From interface ` https://developer.android.com/reference/java/io/Closeable ` |---|---| | ` abstract void` | ` https://developer.android.com/reference/java/io/Closeable#close()() ` Closes this stream and releases any system resources associated with it. | ||
| From interface ` https://developer.android.com/reference/java/lang/AutoCloseable ` |---|---| | ` abstract void` | ` https://developer.android.com/reference/java/lang/AutoCloseable#close()() ` Closes this resource, relinquishing any underlying resources. | ||
## Protected constructors
### SelectableChannel
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
protected SelectableChannel ()
```
Initializes a new instance of this class.
## Public methods
### blockingLock
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract Object blockingLock ()
```
Retrieves the object upon which the `https://developer.android.com/reference/java/nio/channels/SelectableChannel#configureBlocking(boolean)` and `https://developer.android.com/reference/java/nio/channels/SelectableChannel#register(java.nio.channels.Selector,%20int)` methods synchronize.
This is often useful in the implementation of adaptors that require a
specific blocking mode to be maintained for a short period of time.
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/lang/Object` | The blocking-mode lock object
|
### configureBlocking
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract SelectableChannel configureBlocking (boolean block)
```
Adjusts this channel's blocking mode.
If this channel is registered with one or more selectors then an
attempt to place it into blocking mode will cause an `https://developer.android.com/reference/java/nio/channels/IllegalBlockingModeException` to be thrown.
This method may be invoked at any time. The new blocking mode will
only affect I/O operations that are initiated after this method returns.
For some implementations this may require blocking until all pending I/O
operations are complete.
If this method is invoked while another invocation of this method or
of the `https://developer.android.com/reference/java/nio/channels/SelectableChannel#register(java.nio.channels.Selector,%20int)` method is in progress
then it will first block until the other operation is complete.
| Parameters ||
|---|---|
| `block` | `boolean`: If `true` then this channel will be placed in blocking mode; if `false` then it will be placed non-blocking mode
|
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/nio/channels/SelectableChannel` | This selectable channel
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/IOException` | If an I/O error occurs |
| `https://developer.android.com/reference/java/nio/channels/ClosedChannelException` | If this channel is closed |
| `https://developer.android.com/reference/java/nio/channels/IllegalBlockingModeException` | If `block` is `true` and this channel is registered with one or more selectors |
### isBlocking
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract boolean isBlocking ()
```
Tells whether or not every I/O operation on this channel will block
until it completes. A newly-created channel is always in blocking mode.
If this channel is closed then the value returned by this method is
not specified.
| Returns ||
|---|---|
| `boolean` | `true` if, and only if, this channel is in blocking mode
|
### isRegistered
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract boolean isRegistered ()
```
Tells whether or not this channel is currently registered with any
selectors. A newly-created channel is not registered.
Due to the inherent delay between key cancellation and channel
deregistration, a channel may remain registered for some time after all
of its keys have been cancelled. A channel may also remain registered
for some time after it is closed.
| Returns ||
|---|---|
| `boolean` | `true` if, and only if, this channel is registered
|
### keyFor
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract SelectionKey keyFor (Selector sel)
```
Retrieves the key representing the channel's registration with the given
selector.
| Parameters ||
|---|---|
| `sel` | `Selector`: The selector
|
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/nio/channels/SelectionKey` | The key returned when this channel was last registered with the given selector, or `null` if this channel is not currently registered with that selector
|
### provider
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract SelectorProvider provider ()
```
Returns the provider that created this channel.
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/nio/channels/spi/SelectorProvider` | The provider that created this channel
|
### register
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract SelectionKey register (Selector sel,
int ops,
Object att)
```
Registers this channel with the given selector, returning a selection
key.
If this channel is currently registered with the given selector then
the selection key representing that registration is returned. The key's
interest set will have been changed to `ops`, as if by invoking
the `https://developer.android.com/reference/java/nio/channels/SelectionKey#interestOps(int)` method. If
the `att` argument is not `null` then the key's attachment
will have been set to that value. A `https://developer.android.com/reference/java/nio/channels/CancelledKeyException` will
be thrown if the key has already been cancelled.
Otherwise this channel has not yet been registered with the given
selector, so it is registered and the resulting new key is returned.
The key's initial interest set will be `ops` and its attachment
will be `att`.
This method may be invoked at any time. If this method is invoked
while a selection operation is in progress then it has no effect upon
that operation; the new registration or change to the key's interest set
will be seen by the next selection operation. If this method is invoked
while an invocation of `https://developer.android.com/reference/java/nio/channels/SelectableChannel#configureBlocking(boolean)`
is in progress then it will block until the channel's blocking mode has
been adjusted.
If this channel is closed while this operation is in progress then
the key returned by this method will have been cancelled and will
therefore be invalid.
| Parameters ||
|---|---|
| `sel` | `Selector`: The selector with which this channel is to be registered
|
| `ops` | `int`: The interest set for the resulting key
|
| `att` | `Object`: The attachment for the resulting key; may be `null`
|
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/nio/channels/SelectionKey` | A key representing the registration of this channel with the given selector
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | If a bit in the `ops` set does not correspond to an operation that is supported by this channel, that is, if `set & ~validOps() != 0` |
| `https://developer.android.com/reference/java/nio/channels/CancelledKeyException` | If this channel is currently registered with the given selector but the corresponding key has already been cancelled |
| `https://developer.android.com/reference/java/nio/channels/ClosedChannelException` | If this channel is closed |
| `https://developer.android.com/reference/java/nio/channels/ClosedSelectorException` | If the selector is closed |
| `https://developer.android.com/reference/java/nio/channels/IllegalBlockingModeException` | If this channel is in blocking mode |
| `https://developer.android.com/reference/java/nio/channels/IllegalSelectorException` | If this channel was not created by the same provider as the given selector |
### register
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public final SelectionKey register (Selector sel,
int ops)
```
Registers this channel with the given selector, returning a selection
key.
An invocation of this convenience method of the form
> `sc.register(sel, ops)`
behaves in exactly the same way as the invocation `sc.``https://developer.android.com/reference/java/nio/channels/SelectableChannel#register(java.nio.channels.Selector,%20int,%20java.lang.Object)`
| Parameters ||
|---|---|
| `sel` | `Selector`: The selector with which this channel is to be registered
|
| `ops` | `int`: The interest set for the resulting key
|
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/nio/channels/SelectionKey` | A key representing the registration of this channel with the given selector
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | If a bit in `ops` does not correspond to an operation that is supported by this channel, that is, if `set & ~validOps() != 0` |
| `https://developer.android.com/reference/java/nio/channels/CancelledKeyException` | If this channel is currently registered with the given selector but the corresponding key has already been cancelled |
| `https://developer.android.com/reference/java/nio/channels/ClosedChannelException` | If this channel is closed |
| `https://developer.android.com/reference/java/nio/channels/ClosedSelectorException` | If the selector is closed |
| `https://developer.android.com/reference/java/nio/channels/IllegalBlockingModeException` | If this channel is in blocking mode |
| `https://developer.android.com/reference/java/nio/channels/IllegalSelectorException` | If this channel was not created by the same provider as the given selector |
### validOps
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract int validOps ()
```
Returns an [operation set](https://developer.android.com/reference/java/nio/channels/SelectionKey#opsets)
identifying this channel's supported operations. The bits that are set
in this integer value denote exactly the operations that are valid for
this channel. This method always returns the same value for a given
concrete channel class.
| Returns ||
|---|---|
| `int` | The valid-operation set
|