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	/*
	* Copyright (c) 2001, 2013, 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.awt.dnd;

	import java.awt.AWTEventMulticaster;
	import java.io.ObjectOutputStream;
	import java.io.IOException;
	import java.util.EventListener;


	/**
	* A class extends <code>AWTEventMulticaster</code> to implement efficient and
	* thread-safe multi-cast event dispatching for the drag-and-drop events defined
	* in the java.awt.dnd package.
	*
	* @since 1.4
	* @see AWTEventMulticaster
	*/

	class DnDEventMulticaster extends AWTEventMulticaster
	implements DragSourceListener, DragSourceMotionListener {

	/**
	* Creates an event multicaster instance which chains listener-a
	* with listener-b. Input parameters <code>a</code> and <code>b</code>
	* should not be <code>null</code>, though implementations may vary in
	* choosing whether or not to throw <code>NullPointerException</code>
	* in that case.
	*
	* @param a listener-a
	* @param b listener-b
	*/
	protected DnDEventMulticaster(EventListener a, EventListener b) {
	super(a,b);
	}

	/**
	* Handles the <code>DragSourceDragEvent</code> by invoking
	* <code>dragEnter</code> on listener-a and listener-b.
	*
	* @param dsde the <code>DragSourceDragEvent</code>
	*/
	public void dragEnter(DragSourceDragEvent dsde) {
	((DragSourceListener)a).dragEnter(dsde);
	((DragSourceListener)b).dragEnter(dsde);
	}

	/**
	* Handles the <code>DragSourceDragEvent</code> by invoking
	* <code>dragOver</code> on listener-a and listener-b.
	*
	* @param dsde the <code>DragSourceDragEvent</code>
	*/
	public void dragOver(DragSourceDragEvent dsde) {
	((DragSourceListener)a).dragOver(dsde);
	((DragSourceListener)b).dragOver(dsde);
	}

	/**
	* Handles the <code>DragSourceDragEvent</code> by invoking
	* <code>dropActionChanged</code> on listener-a and listener-b.
	*
	* @param dsde the <code>DragSourceDragEvent</code>
	*/
	public void dropActionChanged(DragSourceDragEvent dsde) {
	((DragSourceListener)a).dropActionChanged(dsde);
	((DragSourceListener)b).dropActionChanged(dsde);
	}

	/**
	* Handles the <code>DragSourceEvent</code> by invoking
	* <code>dragExit</code> on listener-a and listener-b.
	*
	* @param dse the <code>DragSourceEvent</code>
	*/
	public void dragExit(DragSourceEvent dse) {
	((DragSourceListener)a).dragExit(dse);
	((DragSourceListener)b).dragExit(dse);
	}

	/**
	* Handles the <code>DragSourceDropEvent</code> by invoking
	* <code>dragDropEnd</code> on listener-a and listener-b.
	*
	* @param dsde the <code>DragSourceDropEvent</code>
	*/
	public void dragDropEnd(DragSourceDropEvent dsde) {
	((DragSourceListener)a).dragDropEnd(dsde);
	((DragSourceListener)b).dragDropEnd(dsde);
	}

	/**
	* Handles the <code>DragSourceDragEvent</code> by invoking
	* <code>dragMouseMoved</code> on listener-a and listener-b.
	*
	* @param dsde the <code>DragSourceDragEvent</code>
	*/
	public void dragMouseMoved(DragSourceDragEvent dsde) {
	((DragSourceMotionListener)a).dragMouseMoved(dsde);
	((DragSourceMotionListener)b).dragMouseMoved(dsde);
	}

	/**
	* Adds drag-source-listener-a with drag-source-listener-b and
	* returns the resulting multicast listener.
	*
	* @param a drag-source-listener-a
	* @param b drag-source-listener-b
	*/
	public static DragSourceListener add(DragSourceListener a,
	DragSourceListener b) {
	return (DragSourceListener)addInternal(a, b);
	}

	/**
	* Adds drag-source-motion-listener-a with drag-source-motion-listener-b and
	* returns the resulting multicast listener.
	*
	* @param a drag-source-motion-listener-a
	* @param b drag-source-motion-listener-b
	*/
	public static DragSourceMotionListener add(DragSourceMotionListener a,
	DragSourceMotionListener b) {
	return (DragSourceMotionListener)addInternal(a, b);
	}

	/**
	* Removes the old drag-source-listener from drag-source-listener-l
	* and returns the resulting multicast listener.
	*
	* @param l drag-source-listener-l
	* @param oldl the drag-source-listener being removed
	*/
	public static DragSourceListener remove(DragSourceListener l,
	DragSourceListener oldl) {
	return (DragSourceListener)removeInternal(l, oldl);
	}

	/**
	* Removes the old drag-source-motion-listener from
	* drag-source-motion-listener-l and returns the resulting multicast
	* listener.
	*
	* @param l drag-source-motion-listener-l
	* @param ol the drag-source-motion-listener being removed
	*/
	public static DragSourceMotionListener remove(DragSourceMotionListener l,
	DragSourceMotionListener ol) {
	return (DragSourceMotionListener)removeInternal(l, ol);
	}

	/**
	* Returns the resulting multicast listener from adding listener-a
	* and listener-b together.
	* If listener-a is null, it returns listener-b;
	* If listener-b is null, it returns listener-a
	* If neither are null, then it creates and returns
	* a new AWTEventMulticaster instance which chains a with b.
	* @param a event listener-a
	* @param b event listener-b
	*/
	protected static EventListener addInternal(EventListener a, EventListener b) {
	if (a == null) return b;
	if (b == null) return a;
	return new DnDEventMulticaster(a, b);
	}

	/**
	* Removes a listener from this multicaster and returns the
	* resulting multicast listener.
	* @param oldl the listener to be removed
	*/
	protected EventListener remove(EventListener oldl) {
	if (oldl == a) return b;
	if (oldl == b) return a;
	EventListener a2 = removeInternal(a, oldl);
	EventListener b2 = removeInternal(b, oldl);
	if (a2 == a && b2 == b) {
	return this; // it's not here
	}
	return addInternal(a2, b2);
	}

	/**
	* Returns the resulting multicast listener after removing the
	* old listener from listener-l.
	* If listener-l equals the old listener OR listener-l is null,
	* returns null.
	* Else if listener-l is an instance of AWTEventMulticaster,
	* then it removes the old listener from it.
	* Else, returns listener l.
	* @param l the listener being removed from
	* @param oldl the listener being removed
	*/
	protected static EventListener removeInternal(EventListener l, EventListener oldl) {
	if (l == oldl \|\| l == null) {
	return null;
	} else if (l instanceof DnDEventMulticaster) {
	return ((DnDEventMulticaster)l).remove(oldl);
	} else {
	return l; // it's not here
	}
	}

	protected static void save(ObjectOutputStream s, String k, EventListener l)
	throws IOException {
	AWTEventMulticaster.save(s, k, l);
	}
	}

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