I filed this bug after seeing it in startup profiles, where isEmpty()
avoids an instanceof and four(!) method calls, so getting rid of a few
of these has a measurable impact on startup. It seemed prudent to just
replace it all while we're at it.
C2 should be able to optimize equals("") to the equivalent of isEmpty()
for hot cases, of course, but those JIT threads are probably better
spent optimizing other things. :-)
/Claes
On 2018-12-06 21:27, Jim Laskey wrote
I assume you automated this change, might be worthwhile to automate a
verification (compare the -+ pairs.) Eyeballing the patch it seems complete,
one comment changed as well.
Question: Is it probably that vm optimizes .equals(“”) to .isEmpty() and there
is no net win, ie., more of an esthetic clean up than for performance?
Cheers,
— Jim
On Dec 6, 2018, at 4:04 PM, Roger Riggs <roger.ri...@oracle.com> wrote:
Please review changing string.equals("") to string.isEmpty().
isEmpty is preferred, performs better and is easier to optimize.
The change is a literal substitution in all files and only in these modules:
java.base
java.logging
java.management
java.management.rmi
java.naming
java.net.http
java.prefs
java.rmi
java.scripting
java.sql
java.sql.rowset
java.xml
jdk.jartool
jdk.javadoc
jdk.jcmd
jdk.jconsole
jdk.management.agent
jdk.naming.dns
jdk.rmic
Webrev:
http://cr.openjdk.java.net/~rriggs/webrev-string-isempty-8214971-1/
Issue:
https://bugs.openjdk.java.net/browse/JDK-8214971
Thanks, Roger
