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	/*
	* Copyright (c) 1997, 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 javax.swing.tree;

	import javax.swing.event.*;

	/**
	* The model used by <code>JTree</code>.
	* <p>
	* <code>JTree</code> and its related classes make extensive use of
	* <code>TreePath</code>s for identifying nodes in the <code>TreeModel</code>.
	* If a <code>TreeModel</code> returns the same object, as compared by
	* <code>equals</code>, at two different indices under the same parent
	* than the resulting <code>TreePath</code> objects will be considered equal
	* as well. Some implementations may assume that if two
	* <code>TreePath</code>s are equal, they identify the same node. If this
	* condition is not met, painting problems and other oddities may result.
	* In other words, if <code>getChild</code> for a given parent returns
	* the same Object (as determined by <code>equals</code>) problems may
	* result, and it is recommended you avoid doing this.
	* <p>
	* Similarly <code>JTree</code> and its related classes place
	* <code>TreePath</code>s in <code>Map</code>s. As such if
	* a node is requested twice, the return values must be equal
	* (using the <code>equals</code> method) and have the same
	* <code>hashCode</code>.
	* <p>
	* For further information on tree models,
	* including an example of a custom implementation,
	* see <a
	href="https://docs.oracle.com/javase/tutorial/uiswing/components/tree.html">How to Use Trees</a>
	* in <em>The Java Tutorial.</em>
	*
	* @see TreePath
	*
	* @author Rob Davis
	* @author Ray Ryan
	*/
	public interface TreeModel
	{

	/**
	* Returns the root of the tree. Returns <code>null</code>
	* only if the tree has no nodes.
	*
	* @return the root of the tree
	*/
	public Object getRoot();


	/**
	* Returns the child of <code>parent</code> at index <code>index</code>
	* in the parent's
	* child array. <code>parent</code> must be a node previously obtained
	* from this data source. This should not return <code>null</code>
	* if <code>index</code>
	* is a valid index for <code>parent</code> (that is <code>index >= 0 &&
	* index < getChildCount(parent</code>)).
	*
	* @param parent a node in the tree, obtained from this data source
	* @return the child of <code>parent</code> at index <code>index</code>
	*/
	public Object getChild(Object parent, int index);


	/**
	* Returns the number of children of <code>parent</code>.
	* Returns 0 if the node
	* is a leaf or if it has no children. <code>parent</code> must be a node
	* previously obtained from this data source.
	*
	* @param parent a node in the tree, obtained from this data source
	* @return the number of children of the node <code>parent</code>
	*/
	public int getChildCount(Object parent);


	/**
	* Returns <code>true</code> if <code>node</code> is a leaf.
	* It is possible for this method to return <code>false</code>
	* even if <code>node</code> has no children.
	* A directory in a filesystem, for example,
	* may contain no files; the node representing
	* the directory is not a leaf, but it also has no children.
	*
	* @param node a node in the tree, obtained from this data source
	* @return true if <code>node</code> is a leaf
	*/
	public boolean isLeaf(Object node);

	/**
	* Messaged when the user has altered the value for the item identified
	* by <code>path</code> to <code>newValue</code>.
	* If <code>newValue</code> signifies a truly new value
	* the model should post a <code>treeNodesChanged</code> event.
	*
	* @param path path to the node that the user has altered
	* @param newValue the new value from the TreeCellEditor
	*/
	public void valueForPathChanged(TreePath path, Object newValue);

	/**
	* Returns the index of child in parent. If either <code>parent</code>
	* or <code>child</code> is <code>null</code>, returns -1.
	* If either <code>parent</code> or <code>child</code> don't
	* belong to this tree model, returns -1.
	*
	* @param parent a node in the tree, obtained from this data source
	* @param child the node we are interested in
	* @return the index of the child in the parent, or -1 if either
	* <code>child</code> or <code>parent</code> are <code>null</code>
	* or don't belong to this tree model
	*/
	public int getIndexOfChild(Object parent, Object child);

	//
	// Change Events
	//

	/**
	* Adds a listener for the <code>TreeModelEvent</code>
	* posted after the tree changes.
	*
	* @param l the listener to add
	* @see #removeTreeModelListener
	*/
	void addTreeModelListener(TreeModelListener l);

	/**
	* Removes a listener previously added with
	* <code>addTreeModelListener</code>.
	*
	* @see #addTreeModelListener
	* @param l the listener to remove
	*/
	void removeTreeModelListener(TreeModelListener l);

	}

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