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I was going through some of the documentation on Java IO and just wanted to make sure whether I get this right:
Unbuffered Input Streams: FileInputStream, InputStreamReader, FileReader
Unbuffered Output Streams: FileOutputStream, OutputStreamWriter, FileWriter
Buffered Output Streams: PrintStream, PrintWriter
In addition, we have the BufferedInputStream, BufferedOutputStream, BufferedReader and BufferedWriter streams to convert the unbuffered streams into buffered versions.
Finally, I observed that for the Character Streams, viz. InputStreamReader, FileReader, OutputStreamWriter, FileWriter, an internal byte-buffer is maintained for the bytes before they are sent into the stream. This byte-buffer is not under our control. Hence, for Character Streams, buffering refers to the high-level character buffer for storing the characters coming in and going out of the program.
Is everything I said correct?
P.S. - I understand that this buffering issue is somewhat implementation dependent, but I just wish to confirm what the javadocs are saying
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To reduce this kind of overhead, the Java platform implements buffered I/O streams. Buffered input streams read data from a memory area known as a buffer; the native input API is called only when the buffer is empty. Similarly, buffered output streams write data to a buffer, and the native output API is called only when the buffer is full.
Java BufferedOutputStream Class Java BufferedOutputStream class is used for buffering an output stream. It internally uses buffer to store data. It adds more efficiency than to write data directly into a stream.
Similarly, buffered output streams write data to a buffer, and the native output API is called only when the buffer is full. A program can convert an unbuffered stream into a buffered stream using the wrapping idiom we've used several times now, where the unbuffered stream object is passed to the constructor for a buffered stream class.
Buffered input streams read data from a memory area known as a buffer; the native input API is called only when the buffer is empty. Similarly, buffered output streams write data to a buffer, and the native output API is called only when the buffer is full.
Rules of thumb:
Any InputStream / Reader that reads directly from an external source (FileInputStream, SocketInputStream, etc.) is 'raw' and considered unbuffered. (Though in reality, there is probably some buffering going on, depends on the implementation)
Any 'raw' InputStream or Reader can be buffered by a BufferedInputStream or BufferedReader.
Same assumptions for OuputStreams / Writers.
Other stream decorators (i.e. GZIPInputStream, MD5InputStream, YourSpecialObjectWriter) probably do some buffering, but its not very harmful to buffer the source.
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