Noobish "efficiency" question on DataOutputStream

So, I currently have this:
byte[] buf = some_bytes;
DataOutputStream out = new DataOutputStream(socket.getOutputStream());
out.writeInt(buf.length);
out.write(buf);I've always thought that calling write(byte[]) and any given OutputStream will be "efficient", in that things will be chunked under the hood to avoid incurring whatever I/O overhead is present for each and every byte. So, as I understand it, we only need to explicitly use BufferedOutputStream if we're writing one or a few bytes at a time.
Now I'm not so sure.
Digging through the core API source code a bit, it seems that this ultimately calls OutputStream.write(byte) in a loop, which, presumably, is bad unless the OutputStream in question is a Buffered one.
Am I shooting myself in the foot here? Should I be wrapping that DataOuputStream around a BufferedOutputStream? Or vice versa?
Or should I just scrap the DataOuputStream altogether and write the int's bytes out myself?
I'm going to test it both ways, but in the meantime, and just in case the tests are not definitive, I'm wondering if anybody here can tell me what I should expect to see.
I think I've been staring at this stuff for a bit too long and am second-guessing myself to death here no matter which way I look at it. So thanks in advance for any nudge you can give me back toward sanity.
Edited by: jverd on Feb 16, 2012 3:59 PM

EJP wrote:
So, what's the point of the basic OutputStream not being buffered then?I guess the idea was that if you want buffering you say so,Ok.
I think you'll find that every significant class that extends OutputStream (specifically FileOutputStream and SocketOutputStream) overrides write(byte[], int, int) to do an atomic write to the OS, so it isn't really such an issue except in the case of DataOutputStream (and not ObjectOutputStream, see above).Okay, so, in this case, I've got a DataOutputStream wrapped around a SocketOutputStream. It's not an issue for SOS, but it is for the wrapping DOS. Yes?
So to overcome the DOS doing a bunch of piddly 1-byte writes to the SOS, which in turn could result in a bunch of piddly 1-byte writes to the network, which I don't want, I inject a BOS between them. Yes?
Thanks for the help. I can't believe after all these years I never got these details sorted out. I guess it never came up quite this way before.

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