When does finalize run

Get hold of all the important Java Foundation and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready. Since it is available for every java class hence Garbage Collector can call the finalize method on any java object Why finalize method is used?

JVM allows finalize to be invoked only once per object. Skip to content. Change Language. Related Articles. It is hard to say, but there are a few possibilities: The object is not garbage collected because it is still reachable. The object is not garbage collected because the GC doesn't run before your test finishes. The object is found by the GC and placed in the finalization queue by the GC, but finalization isn't completed before your test finishes.

Stephen C Stephen C k 90 90 gold badges silver badges bronze badges. Difficult to observe so we force JVM to call it by System.

Pls slow down. Calling System. It is also not guaranteed what kind of collection will be run. Relevant since most Java GCs are "generational" collectors. OnaBai Using VisualVM to observe as well as using weak references to track the actual interaction I found that following things are true in a Java 8 environment Oracle JDK, Ubuntu 15 : Finalize is not called immediately the Finalizer GC part individually owns the reference elusively The default Garbage Collector pools unreachable objects Finalize is called in bulk pointing to an implementation detail that there is a certain phase the garbage collector frees the resources.

So if you have a lot of objects getting finalized the finalization phase will be triggered more often and earlier when compared with only a few There were circumstances a System. This might be generation related. Final Thought Finalize method is unreliable but can be used for one thing only. Martin Kersten Martin Kersten 5, 4 4 gold badges 39 39 silver badges 69 69 bronze badges.

Generally an object becomes eligible for garbage collection in Java on following cases: All references of that object explicitly set to null e. Parent object set to null, if an object holds reference of another object and when you set container object's reference null, child or contained object automatically becomes eligible for garbage collection. If an object has only live references via WeakHashMap it will be eligible for garbage collection.

Darin Kolev 3, 13 13 gold badges 30 30 silver badges 45 45 bronze badges. Tushar Trivedi Tushar Trivedi 1 1 gold badge 2 2 silver badges 12 12 bronze badges. If a final field of an object is used repeatedly during a slow computation, and the object will never be used after that, would the object be kept alive until the last the the source code requests the field, or could the JIT copy the field to a temporary variable and then abandon the object before computation?

Holger: In cases where the JIT can see everything that's ever going to happen to an object between its creation and abandonment, I don't see any reason for the JIT to fire the finalizer early.

The real question would be what code needs to do to ensure that the finalizer can't fire within a particular method.

NET there is a GC. KeepAlive function which does nothing except force the GC to assume that it might use an object, but I know of no such function in Java. One could use volatile variable for that purpose, but using a variable solely for such a purpose would seem wasteful.

Synchronization is sufficient to ensure a happens-before relationship; since the finalization may actually is running in a different thread, it often is formally necessary anyway. Java 9 is going to add Reference. Would synchronization code typically be expected for objects which only expect to be used in a single thread?

If an object performs some action that needs to be undone before it's abandoned e. Would it be normal for code to use synchronization Show 2 more comments. Craig S. Anderson 6, 4 4 gold badges 28 28 silver badges 43 43 bronze badges.

What you are saying is that an object is finalized when it becomes unreachable. It is actually called when the method is actually collected.

Amarildo Amarildo 4 4 silver badges 19 19 bronze badges. Meet Doshi 4, 10 10 gold badges 36 36 silver badges 77 77 bronze badges. Java allows objects to implement a method called finalize that might get called.

If the garbage collector doesn't run, the method doesn't get called. In practice, you are highly unlikely to use it in real projects. JavaDev JavaDev 3 3 silver badges 15 15 bronze badges. Example: If your program end before garbage collector occur, then finalize will not execute. Fourat 2, 2 2 gold badges 37 37 silver badges 49 49 bronze badges. AyukNayr AyukNayr 2 2 silver badges 21 21 bronze badges.

Utkarsh Utkarsh 1 1 gold badge 5 5 silver badges 17 17 bronze badges. Fruchtzwerg 9, 12 12 gold badges 38 38 silver badges 44 44 bronze badges. The Overflow Blog. Podcast Explaining the semiconductor shortage, and how it might end.

Win32 namespace that are derived from System. SafeHandle :. SafeFileHandle is a wrapper class for a file handle. SafeMemoryMappedFileHandle is a wrapper class for memory-mapped file handles. SafeMemoryMappedViewHandle is a wrapper class for a pointer to a block of unmanaged memory. SafePipeHandle is a wrapper class for pipe handles. SafeRegistryHandle is a wrapper class for a handle to a registry key.

SafeWaitHandle is a wrapper class for a wait handle. The following example uses the dispose pattern with safe handles instead of overriding the Finalize method.

It defines a FileAssociation class that wraps registry information about the application that handles files with a particular file extension.

The type's protected Dispose method then calls the SafeRegistryHandle. Dispose method to free these two handles. Feedback will be sent to Microsoft: By pressing the submit button, your feedback will be used to improve Microsoft products and services.

Privacy policy. Skip to main content. This browser is no longer supported. Download Microsoft Edge More info. Contents Exit focus mode. Important If a SafeHandle object is available that wraps your unmanaged resource, the recommended alternative is to implement the dispose pattern with a safe handle and not override Finalize. Note The C compiler does not allow you to override the Finalize method. Is this page helpful? To clarify, you likely mean that you set the reference to null.

Also, as stated before, GC does not perform finalization. Fair enough. A blog about Java and its related technologies, the best practices, algorithms, interview questions, scripting languages, and Python. About Me. Contact Us. Privacy policy. Guest Posts. Secure Hash Algorithms. Best Way to Learn Java.

How to Start New Blog. Skip to content. Last Updated: December 26, Java Examples. Table of Contents 1. Other reasons for not using finalize 4. How to use finalize method correctly - Best Practices 1. Notice that finalize is deprecated method. Overriding finalize method A general syntax to override finalize method is given below. In try block In catch block In finally block In try block In catch block In finally block In try block In catch block In finally block Amazing, finalize method has not executed at all for any thread.

Can we force finalize to execute? This method has already been deprecated in JDK, with the following reason — Runtime. Was this post helpful? Let us know if you liked the post. Java puzzle — Why try-catch-finally blocks require braces? Hello Lokesh, Thank You for your previous response.

Now as per your answer finalize is called by is separate thread for it in JVM whose single responsibility is to execute finalize methods for all objects. Two questions — 1- So does it means gc is also calling finalize? Dude fix your post… Some contents are broken Reply. Thank you very much for pointing this out.