RFR: 6988220: java.lang.ObjectName use of String.intern() causes major performance issues at scale (original) (raw)

Dmytro Sheyko dmytro_sheyko at hotmail.com
Fri Feb 24 09:08:50 UTC 2012

Hi,

Though "compareTo" tends to be less efficient than "equals", it offers better type safety.

When we (mistakenly!) compare objects of different type, "equals" silently accepts parameter of wrong type, but returns false. Comparison with "compareTo" is rejected by compiler.

Consider,

String string = ... Date date = ...

if (string.equals(date)) { // always false }

if (string.compareTo(date) == 0) { // compilation error }

Regards, Dmytro

Date: Thu, 23 Feb 2012 10:58:47 -0500 Subject: Re: RFR: 6988220: java.lang.ObjectName use of String.intern() causes major performance issues at scale From: vitalyd at gmail.com To: frederic.parain at oracle.com CC: serviceability-dev at openjdk.java.net; core-libs-dev at openjdk.java.net

Hi Frederic, Just curious - why are you checking string equality via compareTo() instead of equals()? Thanks Sent from my phone On Feb 23, 2012 10:37 AM, "Frederic Parain" <frederic.parain at oracle.com> wrote: > This a simple fix to solve CR 6988220: > http://bugs.sun.com/bugdatabase/viewbug.do?bugid=6988220<http://bugs.sun.com/bugdatabase/viewbug.do?bugid=6988220> > > The use of String.intern() in the ObjectName class prevents > the class the scale well when more than 20K ObjectNames are > managed. The fix simply removes the use of String.intern(), > and uses regular String instead. The Object.equals() method > is modified too to make a regular String comparison. The > complexity of this method now depends on the length of > the ObjectName's canonical name, and is not impacted any > more by the number of ObjectName instances being handled. > > The Webrev: > http://cr.openjdk.java.net/**fparain/6988220/webrev.00/<http://cr.openjdk.java.net/fparain/6988220/webrev.00/> > > I've tested this fix with the jdklang and jdkmanagement > test suites. > > Thanks, > > Fred > > -- > Frederic Parain - Oracle > Grenoble Engineering Center - France > Phone: +33 4 76 18 81 17 > Email: Frederic.Parain at oracle.com > >

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