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	/*
	* Copyright (c) 1994, 2016, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.util;

	/**
	* This class represents an observable object, or "data"
	* in the model-view paradigm. It can be subclassed to represent an
	* object that the application wants to have observed.
	* <p>
	* An observable object can have one or more observers. An observer
	* may be any object that implements interface {@code Observer}. After an
	* observable instance changes, an application calling the
	* {@code Observable}'s {@code notifyObservers} method
	* causes all of its observers to be notified of the change by a call
	* to their {@code update} method.
	* <p>
	* The order in which notifications will be delivered is unspecified.
	* The default implementation provided in the Observable class will
	* notify Observers in the order in which they registered interest, but
	* subclasses may change this order, use no guaranteed order, deliver
	* notifications on separate threads, or may guarantee that their
	* subclass follows this order, as they choose.
	* <p>
	* Note that this notification mechanism has nothing to do with threads
	* and is completely separate from the {@code wait} and {@code notify}
	* mechanism of class {@code Object}.
	* <p>
	* When an observable object is newly created, its set of observers is
	* empty. Two observers are considered the same if and only if the
	* {@code equals} method returns true for them.
	*
	* @author Chris Warth
	* @see java.util.Observable#notifyObservers()
	* @see java.util.Observable#notifyObservers(java.lang.Object)
	* @see java.util.Observer
	* @see java.util.Observer#update(java.util.Observable, java.lang.Object)
	* @since 1.0
	*
	* @deprecated
	* This class and the {@link Observer} interface have been deprecated.
	* The event model supported by {@code Observer} and {@code Observable}
	* is quite limited, the order of notifications delivered by
	* {@code Observable} is unspecified, and state changes are not in
	* one-for-one correspondence with notifications.
	* For a richer event model, consider using the
	* {@link java.beans} package. For reliable and ordered
	* messaging among threads, consider using one of the concurrent data
	* structures in the {@link java.util.concurrent} package.
	* For reactive streams style programming, see the
	* {@link java.util.concurrent.Flow} API.
	*/
	@Deprecated(since="9")
	public class Observable {
	private boolean changed = false;
	private Vector<Observer> obs;

	/** Construct an Observable with zero Observers. */

	public Observable() {
	obs = new Vector<>();
	}

	/**
	* Adds an observer to the set of observers for this object, provided
	* that it is not the same as some observer already in the set.
	* The order in which notifications will be delivered to multiple
	* observers is not specified. See the class comment.
	*
	* @param o an observer to be added.
	* @throws NullPointerException if the parameter o is null.
	*/
	public synchronized void addObserver(Observer o) {
	if (o == null)
	throw new NullPointerException();
	if (!obs.contains(o)) {
	obs.addElement(o);
	}
	}

	/**
	* Deletes an observer from the set of observers of this object.
	* Passing {@code null} to this method will have no effect.
	* @param o the observer to be deleted.
	*/
	public synchronized void deleteObserver(Observer o) {
	obs.removeElement(o);
	}

	/**
	* If this object has changed, as indicated by the
	* {@code hasChanged} method, then notify all of its observers
	* and then call the {@code clearChanged} method to
	* indicate that this object has no longer changed.
	* <p>
	* Each observer has its {@code update} method called with two
	* arguments: this observable object and {@code null}. In other
	* words, this method is equivalent to:
	* <blockquote>{@code
	* notifyObservers(null)}</blockquote>
	*
	* @see java.util.Observable#clearChanged()
	* @see java.util.Observable#hasChanged()
	* @see java.util.Observer#update(java.util.Observable, java.lang.Object)
	*/
	public void notifyObservers() {
	notifyObservers(null);
	}

	/**
	* If this object has changed, as indicated by the
	* {@code hasChanged} method, then notify all of its observers
	* and then call the {@code clearChanged} method to indicate
	* that this object has no longer changed.
	* <p>
	* Each observer has its {@code update} method called with two
	* arguments: this observable object and the {@code arg} argument.
	*
	* @param arg any object.
	* @see java.util.Observable#clearChanged()
	* @see java.util.Observable#hasChanged()
	* @see java.util.Observer#update(java.util.Observable, java.lang.Object)
	*/
	public void notifyObservers(Object arg) {
	/*
	* a temporary array buffer, used as a snapshot of the state of
	* current Observers.
	*/
	Object[] arrLocal;

	synchronized (this) {
	/* We don't want the Observer doing callbacks into
	* arbitrary code while holding its own Monitor.
	* The code where we extract each Observable from
	* the Vector and store the state of the Observer
	* needs synchronization, but notifying observers
	* does not (should not). The worst result of any
	* potential race-condition here is that:
	* 1) a newly-added Observer will miss a
	* notification in progress
	* 2) a recently unregistered Observer will be
	* wrongly notified when it doesn't care
	*/
	if (!changed)
	return;
	arrLocal = obs.toArray();
	clearChanged();
	}

	for (int i = arrLocal.length-1; i>=0; i--)
	((Observer)arrLocal[i]).update(this, arg);
	}

	/**
	* Clears the observer list so that this object no longer has any observers.
	*/
	public synchronized void deleteObservers() {
	obs.removeAllElements();
	}

	/**
	* Marks this {@code Observable} object as having been changed; the
	* {@code hasChanged} method will now return {@code true}.
	*/
	protected synchronized void setChanged() {
	changed = true;
	}

	/**
	* Indicates that this object has no longer changed, or that it has
	* already notified all of its observers of its most recent change,
	* so that the {@code hasChanged} method will now return {@code false}.
	* This method is called automatically by the
	* {@code notifyObservers} methods.
	*
	* @see java.util.Observable#notifyObservers()
	* @see java.util.Observable#notifyObservers(java.lang.Object)
	*/
	protected synchronized void clearChanged() {
	changed = false;
	}

	/**
	* Tests if this object has changed.
	*
	* @return {@code true} if and only if the {@code setChanged}
	* method has been called more recently than the
	* {@code clearChanged} method on this object;
	* {@code false} otherwise.
	* @see java.util.Observable#clearChanged()
	* @see java.util.Observable#setChanged()
	*/
	public synchronized boolean hasChanged() {
	return changed;
	}

	/**
	* Returns the number of observers of this {@code Observable} object.
	*
	* @return the number of observers of this object.
	*/
	public synchronized int countObservers() {
	return obs.size();
	}
	}

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