NIO : Streams versus blocks

The most important distinction between the original I/O library (found in java.io.* ) and NIO has to do with how data is packaged and transmitted. As previously mentioned, original I/O deals with data in streams, whereas NIO deals with data in blocks.

A stream-oriented I/O system deals with data one byte at a time. An input stream produces one byte of data, and an output stream consumes one byte of data. It is very easy to create filters for streamed data. It is also relatively simply to chain several filters together so that each one does its part in what amounts to a single, sophisticated processing mechanism. On the flip side, stream-oriented I/O is often rather slow.


A block-oriented I/O system deals with data in blocks. Each operation produces or consumes a block of data in one step. Processing data by the block can be much faster than processing it by the (streamed) byte. But block-oriented I/O lacks some of the elegance and simplicity of stream-oriented I/O.