public static final int OP_READ

Operation-set bit for read operations.

Suppose that a selection key's interest set contains OP_READ at the start of a selection operation. If the selector detects that the corresponding channel is ready for reading, has reached end-of-stream, has been remotely shut down for further writing, or has an error pending, then it will add OP_READ to the key's ready-operation set.

public static final int OP_WRITE

Operation-set bit for write operations.

Suppose that a selection key's interest set contains OP_WRITE at the start of a selection operation. If the selector detects that the corresponding channel is ready for writing, has been remotely shut down for further reading, or has an error pending, then it will add OP_WRITE to the key's ready set.

public static final int OP_CONNECT

Operation-set bit for socket-connect operations.

Suppose that a selection key's interest set contains OP_CONNECT at the start of a selection operation. If the selector detects that the corresponding socket channel is ready to complete its connection sequence, or has an error pending, then it will add OP_CONNECT to the key's ready set.

public static final int OP_ACCEPT

Operation-set bit for socket-accept operations.

Suppose that a selection key's interest set contains OP_ACCEPT at the start of a selection operation. If the selector detects that the corresponding server-socket channel is ready to accept another connection, or has an error pending, then it will add OP_ACCEPT to the key's ready set.

protected SelectionKey()

Constructs an instance of this class.

public abstract SelectableChannel channel()

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

public abstract Selector selector()

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

public abstract boolean isValid()

Tells whether or not this key is valid.

A key is valid upon creation and remains so until it is cancelled, its channel is closed, or its selector is closed.

public abstract void cancel()

Requests that the registration of this key's channel with its selector be cancelled. Upon return the key will be invalid and will have been added to its selector's cancelled-key set. The key will be removed from all of the selector's key sets during the next selection operation.

If this key has already been cancelled then invoking this method has no effect. Once cancelled, a key remains forever invalid.

This method may be invoked at any time. It synchronizes on the selector's cancelled-key set, and therefore may block briefly if invoked concurrently with a cancellation or selection operation involving the same selector.

public abstract int interestOps()

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.

public abstract SelectionKey interestOps(int ops)

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

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 change to the key's interest set will be seen by the next selection operation.

public int interestOpsOr(int ops)

Atomically sets this key's interest set to the bitwise union ("or") of the existing interest set and the given value. This method is guaranteed to be atomic with respect to other concurrent calls to this method or to interestOpsAnd(int).

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 change to the key's interest set will be seen by the next selection operation.

public int interestOpsAnd(int ops)

Atomically sets this key's interest set to the bitwise intersection ("and") of the existing interest set and the given value. This method is guaranteed to be atomic with respect to other concurrent calls to this method or to interestOpsOr(int).

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 change to the key's interest set will be seen by the next selection operation.

public abstract int readyOps()

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.

public final boolean isReadable()

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

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

public final boolean isWritable()

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

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

public final boolean isConnectable()

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

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

public final boolean isAcceptable()

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

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

public final Object attach(Object ob)

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.

public final Object attachment()

Retrieves the current attachment.