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public interface AsynchronousChannel extends ChannelA channel that supports asynchronous I/O operations. Asynchronous I/O operations will usually take one of two forms:
void operation(... A attachment,
CompletionHandler<V,? super A> handler)
CompletionHandleris used to consume the result of many I/O operations.
In the first form, the methods defined by the
Futureinterface may be used to check if the operation has completed, wait for its completion, and to retrieve the result. In the second form, a
CompletionHandleris 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 channel's
closemethod 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.
Futureinterface defines the
cancelmethod to cancel execution. This causes all threads waiting on the result of the I/O operation to throw
CancellationException. 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
readoperation 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
writewill fail with an unspecified runtime exception.
cancelmethod is invoked with the
mayInterruptIfRunningparameter set to
truethen 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
CancellationExceptionand any other I/O operations outstanding on the channel complete with the exception
cancelmethod 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.
All Methods Instance Methods Abstract Methods Modifier and Type Method Description
close()Closes this channel.
void 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
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- Specified by:
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IOException- If an I/O error occurs