Am 21.03.2010 20:39, schrieb Martin Buchholz:
On Sun, Mar 21, 2010 at 00:56, Martin Buchholz<[email protected]> wrote:
Study also:
http://code.google.com/p/google-collections/source/browse/trunk/src/com/google/common/base/Preconditions.java
Sorry, the best (most recent) version of Preconditions to study is here:
http://code.google.com/p/guava-libraries/source/browse/trunk/src/com/google/common/base/Preconditions.java
especially this comment:
Thanks for the update. I'm not sure if I understand right the below
comment. Does it mean, that inlining the message from a constant is less
fast than from a call on badMsg()?
-Ulf
/*
* All recent hotspots (as of 2009) *really* like to have the natural code
*
* if (guardExpression) {
* throw new BadException(messageExpression);
* }
*
* refactored so that messageExpression is moved to a separate
* String-returning method.
*
* if (guardExpression) {
* throw new BadException(badMsg(...));
* }
*
* The alternative natural refactorings into void or Exception-returning
* methods are much slower. This is a big deal - we're talking factors of
* 2-8 in microbenchmarks, not just 10-20%. (This is a hotspot optimizer
* bug, which should be fixed, but that's a separate, big project).
*
* The coding pattern above is heavily used in java.util, e.g. in ArrayList.
* There is a RangeCheckMicroBenchmark in the JDK that was used to test this.
*
* But the methods in this class want to throw different exceptions,
* depending on the args, so it appears that this pattern is not directly
* applicable. But we can use the ridiculous, devious trick of throwing an
* exception in the middle of the construction of another exception.
* Hotspot is fine with that.
*/
Martin
