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Finalize method?

srikanth reddy
Ranch Hand

Joined: Jul 28, 2005
Posts: 252
hi frnds ,

i have a doubt .In Khalid mughal books there was a question on finalize method .i wanted to know that the overriding finalize method can it throw both the checked and unchecked exceptions .In the book the explanation was
that it cant throw checked exceptions .

i wanted to know that the definition for it is
protected void finalize() throws Throwable ...

so i think it should throw both checked and unchecked exceptions..

please clarify my doubt ..



Thanks & Regards<br /> <br />-Srikanth
Roja Rani

Joined: Sep 28, 2005
Posts: 22

I have written finalize method that is throwing checked exception, I am not getting any compiler error.
Priya Jothi
Ranch Hand

Joined: Jul 13, 2004
Posts: 168
Hi Srikanth,

Where do u find finalize method definition like this?.

protected void finalize() throws Throwable

It can't be!!.Refer to Object class in Java API.Finalize method is inherited to all other classes only thru this topmost "Object" class.

It should be like this..

protected void finalize()

So if u throw any Unchecked exception compiler doesn't care..where as it'll disallow from throwing any checked exception to prevent overriding rules violation.


Priya Jothi
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Joined: Jul 13, 2004
Posts: 168

Forgot to refer the method details in the is throwing Throwable..So it'll allow.Have tried throwing an is getting compiled.

Raghuveer Kumarakrishnan
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Joined: Mar 13, 2005
Posts: 32

protected void finalize() throws Throwable

Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. A subclass overrides the finalize method to dispose of system resources or to perform other cleanup.

The general contract of finalize is that it is invoked if and when the JavaTM virtual machine has determined that there is no longer any means by which this object can be accessed by any thread that has not yet died, except as a result of an action taken by the finalization of some other object or class which is ready to be finalized. The finalize method may take any action, including making this object available again to other threads; the usual purpose of finalize, however, is to perform cleanup actions before the object is irrevocably discarded. For example, the finalize method for an object that represents an input/output connection might perform explicit I/O transactions to break the connection before the object is permanently discarded.

The finalize method of class Object performs no special action; it simply returns normally. Subclasses of Object may override this definition.

The Java programming language does not guarantee which thread will invoke the finalize method for any given object. It is guaranteed, however, that the thread that invokes finalize will not be holding any user-visible synchronization locks when finalize is invoked. If an uncaught exception is thrown by the finalize method, the exception is ignored and finalization of that object terminates.

After the finalize method has been invoked for an object, no further action is taken until the Java virtual machine has again determined that there is no longer any means by which this object can be accessed by any thread that has not yet died, including possible actions by other objects or classes which are ready to be finalized, at which point the object may be discarded.

The finalize method is never invoked more than once by a Java virtual machine for any given object.

Any exception thrown by the finalize method causes the finalization of this object to be halted, but is otherwise ignored.

Throwable - the Exception raised by this method

Raghu<br />SCJP 1.4<br />SCWCD 1.4<br />SCBCD 1.3
ganga prabhu

Joined: Sep 29, 2005
Posts: 10
Why designers keep finalize method as protected rather than public
A Kumar
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Joined: Jul 04, 2004
Posts: 980

It says that in your finalize method...

you can have try catch block for your checked exception...

When the execution is in progress and exception is raised
and if the exception is handled...then normal completion of method occurs and the object further goes for GC.

If during execution an exception and it is not handled ...then the run time
environment terminates further execution of finalize method ignoring the exception and this object is further eligible for GC..

Hope you get it..
[ October 05, 2005: Message edited by: A Kumar ]
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