Attaches the given object to this key.

  Attaches the given object to this key.

An attached object may later be retrieved via the attachment method. Only one object may be attached at a time; invoking this method causes any previous attachment to be discarded. The current attachment may be discarded by attaching null.

Returns: The previously-attached object, if any, otherwise null
Parameters:
- ob - The object to be attached; may be null

  Retrieves the current attachment.

  Retrieves the current attachment.

Returns: The object currently attached to this key, or null if there is no attachment

  Returns the channel for which this key was created.

  Returns the channel for which this key was created. This method will
continue to return the channel even after the key is cancelled.

Returns: This key's channel

  Retrieves this key's interest set.

  Retrieves this key's interest set.

It is guaranteed that the returned set will only contain operation bits that are valid for this key's channel.

This method may be invoked at any time. Whether or not it blocks, and for how long, is implementation-dependent.

Returns: This key's interest set
Throws:
- CancelledKeyException - If this key has been cancelled

  Sets this key's interest set to the given value.

  Sets this key's interest set to the given value.

This method may be invoked at any time. Whether or not it blocks, and for how long, is implementation-dependent.

Returns: This selection key
Parameters:
- ops - The new interest set
Throws:
- IllegalArgumentException - If a bit in the set does not correspond to an operation that is supported by this key's channel, that is, if set & ~(channel().validOps()) != 0
- CancelledKeyException - If this key has been cancelled

  Tests whether this key's channel is ready to accept a new socket connection.

  Tests whether this key's channel is ready to accept a new socket connection.

An invocation of this method of the form k.isAcceptable() behaves in exactly the same way as the expression

 k.readyOps() & OP_ACCEPT != 0

If this key's channel does not support socket-accept operations then this method always returns false.

Returns: true if, and only if, readyOps() & OP_ACCEPT is nonzero
Throws:
- CancelledKeyException - If this key has been cancelled

  Tests whether this key's channel has either finished, or failed to finish, its socket-connection operation.

  Tests whether this key's channel has either finished, or failed to finish, its socket-connection operation.

An invocation of this method of the form k.isConnectable() behaves in exactly the same way as the expression

 k.readyOps() & OP_CONNECT != 0

If this key's channel does not support socket-connect operations then this method always returns false.

Returns: true if, and only if, readyOps() & OP_CONNECT is nonzero
Throws:
- CancelledKeyException - If this key has been cancelled

  Tests whether this key's channel is ready for reading.

  Tests whether this key's channel is ready for reading.

An invocation of this method of the form k.isReadable() behaves in exactly the same way as the expression

 k.readyOps() & OP_READ != 0

If this key's channel does not support read operations then this method always returns false.

Returns: true if, and only if, readyOps() & OP_READ is nonzero
Throws:
- CancelledKeyException - If this key has been cancelled

  Tests whether this key's channel is ready for writing.

  Tests whether this key's channel is ready for writing.

An invocation of this method of the form k.isWritable() behaves in exactly the same way as the expression

 k.readyOps() & OP_WRITE != 0

If this key's channel does not support write operations then this method always returns false.

Returns: true if, and only if, readyOps() & OP_WRITE is nonzero
Throws:
- CancelledKeyException - If this key has been cancelled

  Retrieves this key's ready-operation set.

  Retrieves this key's ready-operation set.

It is guaranteed that the returned set will only contain operation bits that are valid for this key's channel.

Returns: This key's ready-operation set
Throws:
- CancelledKeyException - If this key has been cancelled

  Returns the selector for which this key was created.

  Returns the selector for which this key was created. This method will
continue to return the selector even after the key is cancelled.

Returns: This key's selector