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CompletionHandler is used to consume the result
of many I/O operations.
In the first form, the methods defined by the
interface may be used to check if the operation has completed, wait for its
completion, and to retrieve the result. In the second form, a
CompletionHandler is invoked to consume the result of the I/O operation when
it completes or fails.
A channel that implements this interface is asynchronously
closeable: If an I/O operation is outstanding on the channel and the
close method is invoked, then the I/O operation
fails with the exception
Asynchronous channels are safe for use by multiple concurrent threads. Some channel implementations may support concurrent reading and writing, but may not allow more than one read and one write operation to be outstanding at any given time.
Future interface defines the
method to cancel execution. This causes all threads waiting on the result of
the I/O operation to throw
Whether the underlying I/O operation can be cancelled is highly implementation
specific and therefore not specified. Where cancellation leaves the channel,
or the entity to which it is connected, in an inconsistent state, then the
channel is put into an implementation specific error state that
prevents further attempts to initiate I/O operations that are similar
to the operation that was cancelled. For example, if a read operation is
cancelled but the implementation cannot guarantee that bytes have not been
read from the channel then it puts the channel into an error state; further
attempts to initiate a
read operation cause an unspecified runtime
exception to be thrown. Similarly, if a write operation is cancelled but the
implementation cannot guarantee that bytes have not been written to the
channel then subsequent attempts to initiate a
write will fail with
an unspecified runtime exception.
cancel method is invoked with the
mayInterruptIfRunning parameter set to
true then the I/O operation
may be interrupted by closing the channel. In that case all threads waiting
on the result of the I/O operation throw
any other I/O operations outstanding on the channel complete with the
cancel method is invoked to cancel read or write
operations then it is recommended that all buffers used in the I/O operations
be discarded or care taken to ensure that the buffers are not accessed while
the channel remains open.
closevoid close() throws IOExceptionCloses this channel.
Any outstanding asynchronous operations upon this channel will complete with the exception
AsynchronousCloseException. After a channel is closed, further attempts to initiate asynchronous I/O operations complete immediately with cause
This method otherwise behaves exactly as specified by the