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a question regarding exception handling in GC.

sura watthana
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Joined: Sep 13, 2004
Posts: 77
Hi,
I have a statement from a book which seems to contradict each other, could somebody please tell me what the statement is trying to say or what it really means? thanks

When the garbage collector calls the finalize() method, it will ignore any exceptions thrown by the finalize() method. In all other cases, normal exception handling occurs when an exception is thrown during the execution of the finalize() method, that is, exceptions are not simply ignored.
Inuka Vincit
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Joined: Aug 10, 2004
Posts: 175

finalize

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.


from the horses mouth

http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Object.html


MCP (C# application dev 70-316) 860<br />SCJP 1.4 100% SCJD (URLyBird) 378<br />MAD 100% nuts
Tom Tolman
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Joined: Sep 02, 2004
Posts: 83

In all other cases, normal exception handling occurs when an exception is thrown during the execution of the finalize() method, that is, exceptions are not simply ignored.


I would interpret this to mean that if you call finalize yourself, the method is treated normally, and the exception must be handled explicitly. If the garbage collector calls finalize, it will ignore the thrown exception (although will terminate the finalize method, presumably at the point of the exception)
 
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