# AbstractSelector
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/spi/AbstractSelector#proctors)\|[Methods](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#pubmethods)\|[Protected Methods](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#promethods)\|[Inherited Methods](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#inhmethods)
# AbstractSelector
`
public
abstract
class
AbstractSelector
`
`
``
extends `[Selector](https://developer.android.com/reference/java/nio/channels/Selector)`
``
`
|---|---|----------------------------------------|
| [java.lang.Object](https://developer.android.com/reference/java/lang/Object) |||
| ↳ | [java.nio.channels.Selector](https://developer.android.com/reference/java/nio/channels/Selector) ||
| | ↳ | java.nio.channels.spi.AbstractSelector |
*** ** * ** ***
Base implementation class for selectors.
This class encapsulates the low-level machinery required to implement the interruption of selection operations. A concrete selector class must invoke the[begin](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#begin())and[end](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#end())methods before and after, respectively, invoking an I/O operation that might block indefinitely. In order to ensure that the[end](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#end())method is always invoked, these methods should be used within a`try`...`finally`block:
>
> ```
> try {
> begin();
> // Perform blocking I/O operation here
> ...
> } finally {
> end();
> }
> ```
This class also defines methods for maintaining a selector's cancelled-key set and for removing a key from its channel's key set, and declares the abstract[register](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#register(java.nio.channels.spi.AbstractSelectableChannel,%20int,%20java.lang.Object))method that is invoked by a selectable channel's[register](https://developer.android.com/reference/java/nio/channels/SelectableChannel#register(java.nio.channels.Selector,%20int))method in order to perform the actual work of registering a channel.
## Summary
| ### Protected constructors ||
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---|
| ` `[AbstractSelector](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#AbstractSelector(java.nio.channels.spi.SelectorProvider))`(`[SelectorProvider](https://developer.android.com/reference/java/nio/channels/spi/SelectorProvider)` provider) ` Initializes a new instance of this class. |
| ### Public methods ||
|-------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------|
| ` final void` | ` `[close](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#close())`() ` Closes this selector. |
| ` final boolean` | ` `[isOpen](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#isOpen())`() ` Tells whether or not this selector is open. |
| ` final `[SelectorProvider](https://developer.android.com/reference/java/nio/channels/spi/SelectorProvider) | ` `[provider](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#provider())`() ` Returns the provider that created this channel. |
| ### Protected methods ||
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| ` final void` | ` `[begin](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#begin())`() ` Marks the beginning of an I/O operation that might block indefinitely. |
| ` final `[Set](https://developer.android.com/reference/java/util/Set)`<`[SelectionKey](https://developer.android.com/reference/java/nio/channels/SelectionKey)`>` | ` `[cancelledKeys](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#cancelledKeys())`() ` Retrieves this selector's cancelled-key set. |
| ` final void` | ` `[deregister](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#deregister(java.nio.channels.spi.AbstractSelectionKey))`(`[AbstractSelectionKey](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelectionKey)` key) ` Removes the given key from its channel's key set. |
| ` final void` | ` `[end](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#end())`() ` Marks the end of an I/O operation that might block indefinitely. |
| ` abstract void` | ` `[implCloseSelector](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#implCloseSelector())`() ` Closes this selector. |
| ` abstract `[SelectionKey](https://developer.android.com/reference/java/nio/channels/SelectionKey) | ` `[register](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#register(java.nio.channels.spi.AbstractSelectableChannel,%20int,%20java.lang.Object))`(`[AbstractSelectableChannel](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelectableChannel)` ch, int ops, `[Object](https://developer.android.com/reference/java/lang/Object)` att) ` Registers the given channel with this selector. |
| ### Inherited methods |
|-----------------------|---|
| From class` `[java.nio.channels.Selector](https://developer.android.com/reference/java/nio/channels/Selector)` ` |----------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | ` abstract void` | ` `[close](https://developer.android.com/reference/java/nio/channels/Selector#close())`() ` Closes this selector. | | ` abstract boolean` | ` `[isOpen](https://developer.android.com/reference/java/nio/channels/Selector#isOpen())`() ` Tells whether or not this selector is open. | | ` abstract `[Set](https://developer.android.com/reference/java/util/Set)`<`[SelectionKey](https://developer.android.com/reference/java/nio/channels/SelectionKey)`>` | ` `[keys](https://developer.android.com/reference/java/nio/channels/Selector#keys())`() ` Returns this selector's key set. | | ` static `[Selector](https://developer.android.com/reference/java/nio/channels/Selector) | ` `[open](https://developer.android.com/reference/java/nio/channels/Selector#open())`() ` Opens a selector. | | ` abstract `[SelectorProvider](https://developer.android.com/reference/java/nio/channels/spi/SelectorProvider) | ` `[provider](https://developer.android.com/reference/java/nio/channels/Selector#provider())`() ` Returns the provider that created this channel. | | ` int` | ` `[select](https://developer.android.com/reference/java/nio/channels/Selector#select(java.util.function.Consumer))`(`[Consumer](https://developer.android.com/reference/java/util/function/Consumer)`<`[SelectionKey](https://developer.android.com/reference/java/nio/channels/SelectionKey)`> action) ` Selects and performs an action on the keys whose corresponding channels are ready for I/O operations. | | ` int` | ` `[select](https://developer.android.com/reference/java/nio/channels/Selector#select(java.util.function.Consumer,%20long))`(`[Consumer](https://developer.android.com/reference/java/util/function/Consumer)`<`[SelectionKey](https://developer.android.com/reference/java/nio/channels/SelectionKey)`> action, long timeout) ` Selects and performs an action on the keys whose corresponding channels are ready for I/O operations. | | ` abstract int` | ` `[select](https://developer.android.com/reference/java/nio/channels/Selector#select(long))`(long timeout) ` Selects a set of keys whose corresponding channels are ready for I/O operations. | | ` abstract int` | ` `[select](https://developer.android.com/reference/java/nio/channels/Selector#select())`() ` Selects a set of keys whose corresponding channels are ready for I/O operations. | | ` int` | ` `[selectNow](https://developer.android.com/reference/java/nio/channels/Selector#selectNow(java.util.function.Consumer))`(`[Consumer](https://developer.android.com/reference/java/util/function/Consumer)`<`[SelectionKey](https://developer.android.com/reference/java/nio/channels/SelectionKey)`> action) ` Selects and performs an action on the keys whose corresponding channels are ready for I/O operations. | | ` abstract int` | ` `[selectNow](https://developer.android.com/reference/java/nio/channels/Selector#selectNow())`() ` Selects a set of keys whose corresponding channels are ready for I/O operations. | | ` abstract `[Set](https://developer.android.com/reference/java/util/Set)`<`[SelectionKey](https://developer.android.com/reference/java/nio/channels/SelectionKey)`>` | ` `[selectedKeys](https://developer.android.com/reference/java/nio/channels/Selector#selectedKeys())`() ` Returns this selector's selected-key set. | | ` abstract `[Selector](https://developer.android.com/reference/java/nio/channels/Selector) | ` `[wakeup](https://developer.android.com/reference/java/nio/channels/Selector#wakeup())`() ` Causes the first selection operation that has not yet returned to return immediately. | ||
| From class` `[java.lang.Object](https://developer.android.com/reference/java/lang/Object)` ` |--------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | ` `[Object](https://developer.android.com/reference/java/lang/Object) | ` `[clone](https://developer.android.com/reference/java/lang/Object#clone())`() ` Creates and returns a copy of this object. | | ` boolean` | ` `[equals](https://developer.android.com/reference/java/lang/Object#equals(java.lang.Object))`(`[Object](https://developer.android.com/reference/java/lang/Object)` obj) ` Indicates whether some other object is "equal to" this one. | | ` void` | ` `[finalize](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 `[Class](https://developer.android.com/reference/java/lang/Class)`` | ` `[getClass](https://developer.android.com/reference/java/lang/Object#getClass())`() ` Returns the runtime class of this`Object`. | | ` int` | ` `[hashCode](https://developer.android.com/reference/java/lang/Object#hashCode())`() ` Returns a hash code value for the object. | | ` final void` | ` `[notify](https://developer.android.com/reference/java/lang/Object#notify())`() ` Wakes up a single thread that is waiting on this object's monitor. | | ` final void` | ` `[notifyAll](https://developer.android.com/reference/java/lang/Object#notifyAll())`() ` Wakes up all threads that are waiting on this object's monitor. | | ` `[String](https://developer.android.com/reference/java/lang/String) | ` `[toString](https://developer.android.com/reference/java/lang/Object#toString())`() ` Returns a string representation of the object. | | ` final void` | ` `[wait](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` | ` `[wait](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` | ` `[wait](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` `[java.io.Closeable](https://developer.android.com/reference/java/io/Closeable)` ` |------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------| | ` abstract void` | ` `[close](https://developer.android.com/reference/java/io/Closeable#close())`() ` Closes this stream and releases any system resources associated with it. | ||
| From interface` `[java.lang.AutoCloseable](https://developer.android.com/reference/java/lang/AutoCloseable)` ` |------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------| | ` abstract void` | ` `[close](https://developer.android.com/reference/java/lang/AutoCloseable#close())`() ` Closes this resource, relinquishing any underlying resources. | ||
## Protected constructors
### AbstractSelector
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
protected AbstractSelector (SelectorProvider provider)
```
Initializes a new instance of this class.
| Parameters ||
|------------|--------------------------------------------------------------------|
| `provider` | `SelectorProvider`: The provider that created this selector
|
## Public methods
### close
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public final void close ()
```
Closes this selector.
If the selector has already been closed then this method returns immediately. Otherwise it marks the selector as closed and then invokes the[implCloseSelector](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#implCloseSelector())method in order to complete the close operation.
| Throws ||
|----------------------------------------------------------------------------|------------------------|
| [IOException](https://developer.android.com/reference/java/io/IOException) | If an I/O error occurs |
### isOpen
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public final boolean isOpen ()
```
Tells whether or not this selector is open.
| Returns ||
|-----------|-----------------------------------------------------|
| `boolean` | `true`if, and only if, this selector is open
|
### provider
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public final SelectorProvider provider ()
```
Returns the provider that created this channel.
| Returns ||
|----------------------------------------------------------------------------------------------------|-----------------------------------------------|
| [SelectorProvider](https://developer.android.com/reference/java/nio/channels/spi/SelectorProvider) | The provider that created this channel
|
## Protected methods
### begin
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
protected final void begin ()
```
Marks the beginning of an I/O operation that might block indefinitely.
This method should be invoked in tandem with the[end](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#end())method, using a`try`...`finally`block as shown[above](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#be), in order to implement interruption for this selector.
Invoking this method arranges for the selector's[wakeup](https://developer.android.com/reference/java/nio/channels/Selector#wakeup())method to be invoked if a thread's[interrupt](https://developer.android.com/reference/java/lang/Thread#interrupt())method is invoked while the thread is blocked in an I/O operation upon the selector.
### cancelledKeys
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
protected final Set cancelledKeys ()
```
Retrieves this selector's cancelled-key set.
This set should only be used while synchronized upon it.
| Returns ||
|----------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------|
| [Set](https://developer.android.com/reference/java/util/Set)`<`[SelectionKey](https://developer.android.com/reference/java/nio/channels/SelectionKey)`>` | The cancelled-key set
|
### deregister
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
protected final void deregister (AbstractSelectionKey key)
```
Removes the given key from its channel's key set.
This method must be invoked by the selector for each channel that it deregisters.
| Parameters ||
|-------|----------------------------------------------------------------|
| `key` | `AbstractSelectionKey`: The selection key to be removed
|
### end
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
protected final void end ()
```
Marks the end of an I/O operation that might block indefinitely.
This method should be invoked in tandem with the[begin](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#begin())method, using a`try`...`finally`block as shown[above](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#be), in order to implement interruption for this selector.
### implCloseSelector
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
protected abstract void implCloseSelector ()
```
Closes this selector.
This method is invoked by the[close](https://developer.android.com/reference/java/nio/channels/spi/AbstractSelector#close())method in order to perform the actual work of closing the selector. This method is only invoked if the selector has not yet been closed, and it is never invoked more than once.
An implementation of this method must arrange for any other thread that is blocked in a selection operation upon this selector to return immediately as if by invoking the[wakeup](https://developer.android.com/reference/java/nio/channels/Selector#wakeup())method.
| Throws ||
|----------------------------------------------------------------------------|---------------------------------------------------|
| [IOException](https://developer.android.com/reference/java/io/IOException) | If an I/O error occurs while closing the selector |
### register
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
protected abstract SelectionKey register (AbstractSelectableChannel ch,
int ops,
Object att)
```
Registers the given channel with this selector.
This method is invoked by a channel's[register](https://developer.android.com/reference/java/nio/channels/SelectableChannel#register(java.nio.channels.Selector,%20int))method in order to perform the actual work of registering the channel with this selector.
| Parameters ||
|-------|------------------------------------------------------------------|
| `ch` | `AbstractSelectableChannel`: The channel to be registered
|
| `ops` | `int`: The initial interest set, which must be valid
|
| `att` | `Object`: The initial attachment for the resulting key
|
| Returns ||
|----------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------|
| [SelectionKey](https://developer.android.com/reference/java/nio/channels/SelectionKey) | A new key representing the registration of the given channel with this selector
|