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POinterrupt all threads in Java in shutdown hook
 

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  1. POinterrupt all threads in Java in shutdown hook
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    <p>I have a simple java program that creates a series of temporary files stored in a local tmp directory. I have added a simple shutdown hook that walks through all files and deletes them, then deletes the tmp directory, before exiting the program. here is the code:</p> <pre><code>Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() { @Override public void run() { File tmpDir = new File("tmp/"); for (File f : tmpDir.listFiles()) { f.delete(); } tmpDir.delete(); } })); </code></pre> <p>My problem is that the thread that creates these files may not have terminated upon launch of the shutdown hook, and therefore, there may be a file created after <code>listFiles()</code> is called. this causes the tmp dir not to get deleted. I have come up with 2 hacks around this:</p> <p>Hack # 1:</p> <pre><code>Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() { @Override public void run() { File tmpDir = new File("tmp/"); while (!tmp.delete()){ for (File f : tmpDir.listFiles()) { f.delete(); } } } })); </code></pre> <p>Hack # 2:</p> <pre><code>Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() { @Override public void run() { try{ Thread.sleep(1000); } catch(InterruptedException e){ e.printStackTrace(); } File tmpDir = new File("tmp/"); for (File f : tmpDir.listFiles()) { f.delete(); } tmpDir.delete(); } })); </code></pre> <p>Neither is a particularly good solution. What would be ideal is to have the shutdown hook wait until all threads have terminated before continuing. Does anyone know if this can be done?</p>
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    1. COWhat about having each thread clean up its own temp files? I've found it helpful to have the same class responsible for creating and deleting its own temp files.
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    2. COWhat results do you get from [`File.deleteOnExit()`](http://docs.oracle.com/javase/6/docs/api/java/io/File.html#deleteOnExit())? It seems like the "normal termination" requirement would apply equally to this as to shutdown hook execution.
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    3. CO@erickson `File.deleteOnExit();` works for the subfiles, but does not work for the tmp directory. presumably the reason is there is no guarantee that all subfiles will be deleted prior to the directory attempting to be deleted. this leads to a nonempty directory, which java cannot delete.
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