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From: markspace <markspace@nospam.nospam>
Newsgroups: comp.lang.java.programmer
Subject: Re: byte stream vs char stream buffer
Date: Fri, 16 May 2014 17:36:31 -0700
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On 5/16/2014 4:55 PM, Roedy Green wrote:

> // ?
> ByteBuffer b2 = bb.slice();

Yes, this bit of code was an amalgam of other bits that I had saved to 
remind myself how to perform some common operations on ByteBuffers.  The 
longer sequence went something like:

       readToCapacity( fc, bb );
       bb.flip();
       ByteBuffer b2 = bb.slice();
       b2.limit( 100 );
       b2.asReadOnlyBuffer();
       readHeader( b2 );
       readFile( bb );

And it was just a way to be able to isolate the (100 byte) header from 
the rest of the stream, as well as be able to retain all original bytes 
without a potentially expensive seek operation.  Mostly just as a 
reminder how to slice up a ByteBuffer into smaller buffers so they can 
be read independently.

 > // request the next chunk of data
 > bb.flip();
 >

BTW, I'd make that comment "reset limit and position for reading" rather 
than "next chuck" (the next chunk would probably be clear(), because if 
the buffer isn't full you'd run into problems with limit using flip()).

Flip() is used to switch from put()s to get()s.  See the docs:

http://docs.oracle.com/javase/7/docs/api/java/nio/Buffer.html#flip()