JVM GC and unused references
Let's say there are following four objects in a Java program:
- main
- a
- b
- c
The dependencies are as follows:
main ==> a ==> b ==> c
In other words, main uses a, a uses b, b uses c.
Now, value of object a changes from reference to b to null. What it means is that there are no active references to b, making it available for garbage collection:
main ==> a =/=> b ==> c
What could happen now:
A) In laymans terms, b can be garbage collected at any time. My assumption is that c will become elligible for gargabe collection only after b is garbage collected.
B) However, I imagine this could be a case that JVM could somehow distinguish between references to c from GC-eligible and non-GC-eligible objects, and therefore mark c as eligible at the same time as b.
Is the behaviour determined by Java Language Specification, or any JVM-related specification? Or is it left for the JVM implementation to decide?
java garbage-collection jvm
asked Nov 12 at 13:16
automatictester
1,084622
add a comment |
Let's say there are following four objects in a Java program:
- main
- a
- b
- c
The dependencies are as follows:
main ==> a ==> b ==> c
In other words, main uses a, a uses b, b uses c.
Now, value of object a changes from reference to b to null. What it means is that there are no active references to b, making it available for garbage collection:
main ==> a =/=> b ==> c
What could happen now:
A) In laymans terms, b can be garbage collected at any time. My assumption is that c will become elligible for gargabe collection only after b is garbage collected.
B) However, I imagine this could be a case that JVM could somehow distinguish between references to c from GC-eligible and non-GC-eligible objects, and therefore mark c as eligible at the same time as b.
Is the behaviour determined by Java Language Specification, or any JVM-related specification? Or is it left for the JVM implementation to decide?
java garbage-collection jvm
asked Nov 12 at 13:16
automatictester
1,084622
1
Some related questions: stackoverflow.com/questions/31451346/…, stackoverflow.com/questions/8812635/…, and stackoverflow.com/questions/10587868/…
– Slaw
Nov 12 at 13:23
1
All that a garbage collector cares for, is thatmainandaare still reachable. Everything else is garbage. Despite its misleading name, a garbage collector never looks at the garbage.
– Holger
Nov 12 at 16:03
add a comment |
Let's say there are following four objects in a Java program:
- main
- a
- b
- c
The dependencies are as follows:
main ==> a ==> b ==> c
In other words, main uses a, a uses b, b uses c.
Now, value of object a changes from reference to b to null. What it means is that there are no active references to b, making it available for garbage collection:
main ==> a =/=> b ==> c
What could happen now:
A) In laymans terms, b can be garbage collected at any time. My assumption is that c will become elligible for gargabe collection only after b is garbage collected.
B) However, I imagine this could be a case that JVM could somehow distinguish between references to c from GC-eligible and non-GC-eligible objects, and therefore mark c as eligible at the same time as b.
Is the behaviour determined by Java Language Specification, or any JVM-related specification? Or is it left for the JVM implementation to decide?
java garbage-collection jvm
asked Nov 12 at 13:16
automatictester
1,084622
Let's say there are following four objects in a Java program:
- main
- a
- b
- c
The dependencies are as follows:
main ==> a ==> b ==> c
In other words, main uses a, a uses b, b uses c.
Now, value of object a changes from reference to b to null. What it means is that there are no active references to b, making it available for garbage collection:
main ==> a =/=> b ==> c
What could happen now:
A) In laymans terms, b can be garbage collected at any time. My assumption is that c will become elligible for gargabe collection only after b is garbage collected.
B) However, I imagine this could be a case that JVM could somehow distinguish between references to c from GC-eligible and non-GC-eligible objects, and therefore mark c as eligible at the same time as b.
Is the behaviour determined by Java Language Specification, or any JVM-related specification? Or is it left for the JVM implementation to decide?
java garbage-collection jvm
java garbage-collection jvm
asked Nov 12 at 13:16
automatictester
1,084622
asked Nov 12 at 13:16
automatictester
1,084622
asked Nov 12 at 13:16
automatictester
1,084622
asked Nov 12 at 13:16
automatictester
1,084622
asked Nov 12 at 13:16
automatictester
1,084622
1,084622
1
Some related questions: stackoverflow.com/questions/31451346/…, stackoverflow.com/questions/8812635/…, and stackoverflow.com/questions/10587868/…
– Slaw
Nov 12 at 13:23
1
All that a garbage collector cares for, is thatmainandaare still reachable. Everything else is garbage. Despite its misleading name, a garbage collector never looks at the garbage.
– Holger
Nov 12 at 16:03
add a comment |
1
Some related questions: stackoverflow.com/questions/31451346/…, stackoverflow.com/questions/8812635/…, and stackoverflow.com/questions/10587868/…
– Slaw
Nov 12 at 13:23
1
All that a garbage collector cares for, is thatmainandaare still reachable. Everything else is garbage. Despite its misleading name, a garbage collector never looks at the garbage.
– Holger
Nov 12 at 16:03
1
1
Some related questions: stackoverflow.com/questions/31451346/…, stackoverflow.com/questions/8812635/…, and stackoverflow.com/questions/10587868/…
– Slaw
Nov 12 at 13:23
Some related questions: stackoverflow.com/questions/31451346/…, stackoverflow.com/questions/8812635/…, and stackoverflow.com/questions/10587868/…
– Slaw
Nov 12 at 13:23
1
1
All that a garbage collector cares for, is that
main and a are still reachable. Everything else is garbage. Despite its misleading name, a garbage collector never looks at the garbage.– Holger
Nov 12 at 16:03
All that a garbage collector cares for, is that
main and a are still reachable. Everything else is garbage. Despite its misleading name, a garbage collector never looks at the garbage.– Holger
Nov 12 at 16:03
add a comment |
1 Answer
1
active
oldest
votes
Thanks to this link, I believe option B is correct:
https://www.dynatrace.com/resources/ebooks/javabook/how-garbage-collection-works/
Once b and c are no longer reachable from GC roots, they are both collectible at the same time.
answered Nov 12 at 19:12
automatictester
1,084622
add a comment |
Your Answer
StackExchange.ifUsing("editor", function ()
StackExchange.using("externalEditor", function ()
StackExchange.using("snippets", function ()
StackExchange.snippets.init();
);
);
, "code-snippets");
StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "1"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);
else
createEditor();
);
function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);
);
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53262985%2fjvm-gc-and-unused-references%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
Thanks to this link, I believe option B is correct:
https://www.dynatrace.com/resources/ebooks/javabook/how-garbage-collection-works/
Once b and c are no longer reachable from GC roots, they are both collectible at the same time.
answered Nov 12 at 19:12
automatictester
1,084622
add a comment |
Thanks to this link, I believe option B is correct:
https://www.dynatrace.com/resources/ebooks/javabook/how-garbage-collection-works/
Once b and c are no longer reachable from GC roots, they are both collectible at the same time.
answered Nov 12 at 19:12
automatictester
1,084622
add a comment |
Thanks to this link, I believe option B is correct:
https://www.dynatrace.com/resources/ebooks/javabook/how-garbage-collection-works/
Once b and c are no longer reachable from GC roots, they are both collectible at the same time.
answered Nov 12 at 19:12
automatictester
1,084622
Thanks to this link, I believe option B is correct:
https://www.dynatrace.com/resources/ebooks/javabook/how-garbage-collection-works/
Once b and c are no longer reachable from GC roots, they are both collectible at the same time.
answered Nov 12 at 19:12
automatictester
1,084622
answered Nov 12 at 19:12
automatictester
1,084622
answered Nov 12 at 19:12
automatictester
1,084622
answered Nov 12 at 19:12
automatictester
1,084622
1,084622
add a comment |
add a comment |
Thanks for contributing an answer to Stack Overflow!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Some of your past answers have not been well-received, and you're in danger of being blocked from answering.
Please pay close attention to the following guidance:
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53262985%2fjvm-gc-and-unused-references%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
1
Some related questions: stackoverflow.com/questions/31451346/…, stackoverflow.com/questions/8812635/…, and stackoverflow.com/questions/10587868/…
– Slaw
Nov 12 at 13:23
1
All that a garbage collector cares for, is that
mainandaare still reachable. Everything else is garbage. Despite its misleading name, a garbage collector never looks at the garbage.– Holger
Nov 12 at 16:03