# Interface Channels.SelectableChannelCloser

Enclosing class:
  `Channels`

public static interface Channels.SelectableChannelCloser
An object used to coordinate the closing of a selectable channel created by `readWriteSelectableChannel`.

Since:
  11

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `implCloseChannel(SelectableChannel sc)`
  Closes a selectable channel.
  `void`
  `implReleaseChannel(SelectableChannel sc)`
  Release the file descriptor and any resources for a selectable channel that closed while registered with one or more `Selector`s.

- ## Method Details

  - ### implCloseChannel

    void implCloseChannel(SelectableChannel sc) throws IOException
    Closes a selectable channel.

    This method is invoked by the channel's close method in order to perform the actual work of closing the channel. This method is only invoked if the channel has not yet been closed, and it is never invoked more than once by the channel's close implementation.

    An implementation of this method must arrange for any other thread that is blocked in an I/O operation upon the channel to return immediately, either by throwing an exception or by returning normally. If the channel is `registered` with one or more `Selector`s then the file descriptor should not be released until the `implReleaseChannel` method is invoked.

    Parameters:
      `sc` - The selectable channel
    Throws:
      `IOException` - If an I/O error occurs while closing the file descriptor
    See Also:
      - `AbstractInterruptibleChannel.implCloseChannel()`

  - ### implReleaseChannel

    void implReleaseChannel(SelectableChannel sc) throws IOException
    Release the file descriptor and any resources for a selectable channel that closed while registered with one or more `Selector`s.

    This method is for cases where a channel is closed when `registered` with one or more `Selector`s. A channel may remain registered for some time after it is closed. This method is invoked when the channel is eventually deregistered from the last `Selector` that it was registered with. It is invoked at most once.

    API Note:
      This method is invoked while synchronized on the selector and its selected-key set. Great care must be taken to avoid deadlocks with other threads that also synchronize on these objects.
    Parameters:
      `sc` - The closed selectable channel
    Throws:
      `IOException` - If an I/O error occurs
    See Also:
      - `AbstractSelector.deregister(java.nio.channels.spi.AbstractSelectionKey)`