StreamFinalizer

extends Object

java.lang.Object
↳	com.sun.imageio.stream.StreamFinalizer

Class Overview

Small class to assist in properly closing an ImageInputStream instance prior to garbage collection. The ImageInputStreamImpl class defines a finalize() method, but in a number of its public subclasses (e.g. FileImageInputStream) we override the finalize() method to be empty for performance reasons, and instead rely on the Disposer mechanism for closing/disposing resources. This is fine when one of these classes is instantiated directly (e.g. new FileImageInputStream()) but in the unlikely case where a user defines their own subclass of one of those streams, we need some way to get back to the behavior of ImageInputStreamImpl, which will call close() as part of finalization. Typically an Image{Input,Output}Stream will construct an instance of StreamFinalizer in its constructor if it detects that it has been subclassed by the user. The ImageInputStream instance will hold a reference to the StreamFinalizer, and the StreamFinalizer will hold a reference back to the ImageInputStream from which it was created. When both are no longer reachable, the StreamFinalizer.finalize() method will be called, which will take care of closing down the ImageInputStream. Clearly this is a bit of a hack, but it will likely only be used in the rarest of circumstances: when a user has subclassed one of the public stream classes. (It should be no worse than the old days when the public stream classes had non-empty finalize() methods.)

Summary

Public Constructors
	StreamFinalizer(ImageInputStream stream)

Protected Methods
void	finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.

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Inherited Methods

From class java.lang.Object

Object	clone() Creates and returns a copy of this object.
boolean	equals(Object obj) Indicates whether some other object is "equal to" this one.
void	finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
final Class<?>	getClass() Returns the runtime class of this `Object`.
int	hashCode() Returns a hash code value for the object.
final void	notify() Wakes up a single thread that is waiting on this object's monitor.
final void	notifyAll() Wakes up all threads that are waiting on this object's monitor.
String	toString() Returns a string representation of the object.
final void	wait() Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.
final void	wait(long timeout, int nanos) Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
final void	wait(long timeout) Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.

Public Constructors

public StreamFinalizer (ImageInputStream stream)

Protected Methods

protected void finalize ()

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 Java^TM 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.

Throws

Throwable

Classes