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finalize() is one of the 9 methods in java.lang.Object class. The api docs for the function state:

Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.

  • But what does the finalize() method actually do?
  • What happens if we manually call the finalize() method?
Madeyedexter
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2 Answers2

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it doesn't do anything by default but it gives you an interception point if you want to perform some action

this is the implementation of finalize() in java.lang.Object

  protected void finalize() throws Throwable { }

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.

See Also

Community
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jmj
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  • I think it's worth noting that while nothing particularly prevents `finalize` from resurrecting an object, an object which resurrects itself will often have no way of knowing whether any objects to which it holds references might have their `finalize` methods run at some arbitrary time in the future. – supercat Oct 28 '13 at 21:37
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I think there is one rule: Never, ever, use it in normal situations. Only for educational purposes and for debugging purposes, it is acceptable.

By default, it does nothing. You can override it in order to find out wether your garbage collector is cleaning up the object. But never put cleanup logic in that method. So, it might be useful to find check if you are releasing the memory or not of specific objects, if you are having memory trouble.

Martijn Courteaux
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