garbage-collection

问题 List<String> list = new ArrayList<>(); for (int i = 0; i < 1000; i++) { StringBuilder sb = new StringBuilder(); String string = sb.toString(); string = string.intern() list.add(string); } In the above sample, after invoking string.intern() method, when will the 1000 objects created in heap (sb.toString) be cleared? Edit 1: If there is no guarantee that these objects could be cleared. Assuming that GC haven't run, is it obsolete to use string.intern() itself? (In terms of the memory usage?) Is

问题 A quick question. Say that I have a class implemented as in below example. class Subscriber { private Publisher publisher = new Publisher; public Subscriber() { publisher.SomeEvent += new EventHandler(OnEventFired); } private void OnEventFired(object sender, EventArgs e) { } } And somewhere in the program I have a method that looks like this: public void DoSomething() { Subscriber subscriber = new Subscriber(); } Am I right to expect that this would cause a memory leak since subscriber never

问题 I have an application that cause to creating lots of garbage. First (and almost one) criteria is low GC pause time. I try different GC parameters using visualgc tool (and gc logs). Best parameters are below. -XX:+UseConcMarkSweepGC -Xmx1172M -Xms600M -XX:+UseParNewGC -XX:NewSize=150M My application run on SunOS 10 with Java 1.6.0_21 . Hardware is 2 x CPU quad core (uname -X result is numCPU = 8). Questions are Observing GC behaviours, New objects creating on eden space until eden is full.

问题 how could I request Java garbage collection externally, starting the program from JAR (Windows BAT used)? From the Java code I can do it with System.gc() When running a JNLP distribution, I get this "Java console" turned on from Control Panel / Java / ... and this Java console provides manual garbage collection. But... When I'm running the jar from command-line / bat the java console doesn't seem to open. Couldn't find help with a brief googling, maybe somebody here? 回答1: You can use jconsole

问题 There are many SO questions regarding "how to remove an accidentally added big file from repo", many of them suggesting using git gc command. However, I find it not working for me and I don't know what's going wrong. Here is what I have done: $ git init Initialized empty Git repository in /home/wzyboy/git/myrepo/.git/ $ echo hello >> README $ git add README $ git commit -a -m 'init commit' [master (root-commit) f21783f] init commit 1 file changed, 1 insertion(+) create mode 100644 README $ du

问题 I am starting my java app with the following command line : java -XX:+PrintCommandLineFlags -verbose:gc -XX:+PrintGCDetails \ -XX:+UseConcMarkSweepGC -jar start.jar The JVM enables the following options: -XX:MaxNewSize=87244800 -XX:MaxTenuringThreshold=4 -XX:NewRatio=7 -XX:NewSize=21811200 -XX:OldPLABSize=16 -XX:OldSize=65433600 -XX:+PrintCommandLineFlags -XX:+PrintGC -XX:+PrintGCDetails -XX:+UseCompressedOops -XX:+UseConcMarkSweepGC -XX:+UseParNewGC Can anyone explains me the meaning of

问题 In my studying for OCJP I came across the following question: class CardBoard { Short story = 200; CardBoard go(CardBoard cb) { cb = null; return cb; } public static void main(String[] args) { CardBoard c1 = new CardBoard(); CardBoard c2 = new CardBoard(); CardBoard c3 = c1.go(c2); c1 = null; // do Stuff }} When //doStuff is reached, how many objects are eligible for GC? The correct answer is 2, meaning c1 and its story object. When line //doStuff is reached, c3 is also null. Why isn't it

问题 My question is basically just how to end the Excel.exe process that runs when using excel. In the application I open and use an excel workbook with a couple sheets, then leave them for the user to do as they please, my problem is that my application never lets go of the Excel process. If the application is closed before closing excel, the process ends when excel is closed, otherwise if I close my application after closing excel, the process stays running. I've tried a few things I've found

问题 When I typed: >>> astrd = 123 >>> import sys >>> sys.getrefcount(astrd) 3 >>> I am not getting where is astrd used 3 times ? 回答1: It's not astrd that is referenced three times, but the value 123 . astrd is simply a name for the (immutable) number 123, which can be referenced however many times. Additionally to that, small integers are usually shared: >>> astrd = 123 >>> sys.getrefcount(astrd) 4 >>> j = 123 >>> sys.getrefcount(astrd) 5 In the second assignment, no new integer is created,

问题 When I typed: >>> astrd = 123 >>> import sys >>> sys.getrefcount(astrd) 3 >>> I am not getting where is astrd used 3 times ? 回答1: It's not astrd that is referenced three times, but the value 123 . astrd is simply a name for the (immutable) number 123, which can be referenced however many times. Additionally to that, small integers are usually shared: >>> astrd = 123 >>> sys.getrefcount(astrd) 4 >>> j = 123 >>> sys.getrefcount(astrd) 5 In the second assignment, no new integer is created,