On Jul 14, 2008, at 18:15, Andreas Delmelle wrote:
<snip />
Just quickly ran Jeremias' test-app myself, and on Apple JVM (1.5),
the difference is +/-300ms for a million iterations, but not very
consistent. Sometimes StringBuffer operates slightly faster, other
times it's CharBuffer that wins. I guess the backing implementations
are very closely related anyway, so it's not all that surprising.
It would most definitely be a huge overkill if it is /only/ used for
simple String concatenation. In the context of catching SAX characters
() events, I think the penalty is bound to be limited (maybe even on
the contrary: see below). That is, I don't think I've ever seen a
parser that reports characters one at a time (which would make the
current implementation using CharBuffer very slow). Most SAX parsers
report the characters in reasonably large chunks (as much as possible).
Just for fun, make it:
...
private static final char[] prefix = {' ', 'm', 'y', 'V', 'a', 'l',
'u', 'e', '='};
...
public String runCharBuffer() {
CharBuffer buf = CharBuffer.allocate(1024);
for (int i = 0; i < STEPS; i++) {
buf.put(prefix).put(Integer.toString(i).toCharArray());
}
return buf.rewind().toString();
}
...
On my end, this runs noticeably faster than when passing Strings
(almost 20%). When switching StringBuffer.append() to use char[]
parameters, it runs a tiny bit slower than with Strings... No idea if
this also holds for the Sun, IBM or Apache implementations.
Qua flexibility, the API for a CharBuffer (optionally) offers the
possibility to get a reference to the backing array. For
StringBuffer, we'd have to do something like: sb.toString
().toCharArray(), and IIC, this always yields an independent copy of
the StringBuffer's array, not the array itself. (Note that this
obviously also has its drawbacks; sometimes, you just /need/ an
independent copy...)
Cheers
Andreas
