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    <p>The spec writes:</p> <blockquote> <p>Before the storage for an object is reclaimed by the garbage collector, the Java Virtual Machine will invoke the finalizer of that object.</p> <p>The Java programming language does not specify how soon a finalizer will be invoked, except to say that it will happen before the storage for the object is reused. </p> </blockquote> <p>I read this to mean that the finalizer must have completed before the storage may be reused.</p> <blockquote> <p>The Java programming language does not specify which thread will invoke the finalizer for any given object. </p> <p><em>It is important to note that many finalizer threads may be active (this is sometimes needed on large shared memory multiprocessors), and that if a large connected data structure becomes garbage, all of the finalize methods for every object in that data structure could be invoked at the same time, each finalizer invocation running in a different thread.</em> </p> </blockquote> <p>That is, finalization may occur in the garbage collector thread, in a separate thead, or even a separate thread pool.</p> <p>A JVM is not permitted to simply abort executing a finalizer, and can only use a finite number of threads (threads are operating system resources, and operating systems don't support arbitrarily many threads). Non-terminating finalizers will therefore of necessity starve that thread pool, thereby inhibit collection of any finalizable objects, and cause a memory leak.</p> <p>The following test program confirms this behavior:</p> <pre><code>public class Test { byte[] memoryHog = new byte[1024 * 1024]; @Override protected void finalize() throws Throwable { System.out.println("Finalizing " + this + " in thread " + Thread.currentThread()); for (;;); } public static void main(String[] args) { for (int i = 0; i &lt; 1000; i++) { new Test(); } } } </code></pre> <p>On Oracle JDK 7, this prints:</p> <blockquote> <pre><code>Finalizing tools.Test@1f1fba0 in thread Thread[Finalizer,8,system] Exception in thread "main" java.lang.OutOfMemoryError: Java heap space at tools.Test.&lt;init&gt;(Test.java:5) at tools.Test.main(Test.java:15) </code></pre> </blockquote>
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    1. POwhat will the Finalizer thread do if there is a infinite loop or deadlock in the Java finalize method
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    1. USmeriton
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    1. CO+1, Did more or less the same test, and got the same result. Only one finalizer thread is involved.
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      1. USMarko Topolnik
    2. CO@mriton, what does the meaning of **_It is important to note that many finalizer threads may be active (this is sometimes needed on large shared memory multiprocessors)_**. Does it have any connection with the GC algorithm we chose,such as CMS. And, is there a relationship between the number of Finalizer thread and the GC algorithm.
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    3. COA JVM may do this however it wants, and different JVMs may do it differently. If you are interested in a particular JVM, check its documentation (or more likely, its source code). lpiepiora's anwer appears to indicate that there is always a single finalizer thread in the Oracle JVM, irrespective of the garbage collection algorithm in use.
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