Writing Files - Beginning Java 2 SDK - page 379

Channel

WritableByteChannel

ReadableByteChannel

Can read data into a buffer Can write data from a

buffer.

ScatteringByteChannel ByteChannel GatheringByteChannel

Can read into muliple
buffers.

Can read data into a buffer and
write data from a buffer.

Can write data from
multiple buffers.

Each arrow points from a given interface to an interface that it implements. The ByteChannel
interface simply combines the operations specified by the ReadableByteChannel and
WritableByteChannel interface without declaring any additional methods. The
ScatteringByteChannel interface extends the ReadableByteChannel interface by adding
methods that allow data to be read and distributed amongst several separate buffers in a single
operation. The GatheringByteChannel adds methods to those of the WritableByteChannel to
permit writing from a number of separate buffers in a single operation.

The methods that each channel interface declares are as follows:

Interface Method and Description

ReadableByteChannel int read(ByteBuffer input)

Reads bytes from a channel into the buffer specified by
the argument and returns the number of bytes read, or
-1 if the end of the stream is reached.

WritableByteChannel int write(ByteBuffer output)

Writes bytes from the buffer specified by the argument
to the channel, and returns the number of bytes written.

ByteChannel This interface just inherits methods from the

ReadableByteChannel and
WritableByteChannel interfaces. No additional
methods are declared.

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