<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1251"><base href="x-msg://121/"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">The only useful use case that I've come up with for PhantomReference is to subclass it. In one case it was used as a wrapper so that we'd know when an object was being collected so that we could reap life-cycle information from it. The behaviour was triggered by an JMX control. I suppose there were other ways to do this but given I only wanted to collect when the object was about to be GC'ed.....<div><br></div><div>Regards,</div><div>Kirk</div><div><br><div><div>On 2013-05-30, at 1:32 PM, Dmytro Sheyko <<a href="mailto:dmytro_sheyko@hotmail.com">dmytro_sheyko@hotmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div class="hmmessage" style="font-size: 12pt; font-family: Calibri; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div dir="ltr">Mark,<br><br>You are listed as an author of java.lang.ref classes. So you must know more than others. Could you shed light on this?<br><br>Thank you,<br>Dmytro<br><br><div><hr id="stopSpelling">From:<span class="Apple-converted-space"> </span><a href="mailto:dmytro_sheyko@hotmail.com">dmytro_sheyko@hotmail.com</a><br>To:<span class="Apple-converted-space"> </span><a href="mailto:hotspot-gc-dev@openjdk.java.net">hotspot-gc-dev@openjdk.java.net</a>;<span class="Apple-converted-space"> </span><a href="mailto:core-libs-dev@openjdk.java.net">core-libs-dev@openjdk.java.net</a><br>Subject: PhantomReference: why not cleared by GC when enqueued?<br>Date: Wed, 29 May 2013 14:45:54 +0300<br><br><div dir="ltr">Hello,<br><br>Why phantom references are not automatically cleared by the garbage collector as they are enqueued?<br><br>Keeping phantom reachable objects in heap has some drawbacks:<br>1. At least 2 GC are required in order to reclaim them, even in case when application code pulls references from reference queue and clears them promptly.<br>2. GC pauses are increased since phantom reachable objects are still to be marked.<br><br>On the other hand, benefits are not obvious. How we can use referent if it's not accessible?<br><br>Regards,<br>Dmytro<br><br></div></div></div></div></blockquote></div><br></div></body></html>