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## javax.swing.tree
Interface TreeModel

All Known Implementing Classes:
  DefaultTreeModel

public interface TreeModel

The interface that defines a suitable data model for a `JTree`. For further information on tree models, including an example of a custom implementation, see How to Use Trees in The Java Tutorial.

`JTree` and its related classes make extensive use of `TreePath`s for indentifying nodes in the `TreeModel`. If a `TreeModel` returns the same object, as compared by `equals`, at two different indices under the same parent than the resulting `TreePath` objects will be considered equal as well. Some implementations may assume that if two `TreePath`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 `getChild` for a given parent returns the same Object (as determined by `equals`) problems may result, and it is recommended you avoid doing this.

See Also:
  `TreePath`

Method Summary
`void` | `addTreeModelListener(TreeModelListener l)` Adds a listener for the `TreeModelEvent` posted after the tree changes.
`Object` | `getChild(Object parent, int index)` Returns the child of `parent` at index `index` in the parent's child array.
`int` | `getChildCount(Object parent)` Returns the number of children of `parent`.
`int` | `getIndexOfChild(Object parent, Object child)` Returns the index of child in parent.
`Object` | `getRoot()` Returns the root of the tree.
`boolean` | `isLeaf(Object node)` Returns `true` if `node` is a leaf.
`void` | `removeTreeModelListener(TreeModelListener l)` Removes a listener previously added with `addTreeModelListener`.
`void` | `valueForPathChanged(TreePath path, Object newValue)` Messaged when the user has altered the value for the item identified by `path` to `newValue`.

Method Detail

### getRoot

    public Object getRoot()

  Returns the root of the tree. Returns `null` only if the tree has no nodes.

  Returns:
    the root of the tree

### getChild

    public Object getChild(Object parent,
                           int index)

  Returns the child of `parent` at index `index` in the parent's child array. `parent` must be a node previously obtained from this data source. This should not return `null` if `index` is a valid index for `parent` (that is `index >= 0 && index < getChildCount(parent`)).

  Parameters:
    `parent` - a node in the tree, obtained from this data source
  Returns:
    the child of `parent` at index `index`

### getChildCount

    public int getChildCount(Object parent)

  Returns the number of children of `parent`. Returns 0 if the node is a leaf or if it has no children. `parent` must be a node previously obtained from this data source.

  Parameters:
    `parent` - a node in the tree, obtained from this data source
  Returns:
    the number of children of the node `parent`

### isLeaf

    public boolean isLeaf(Object node)

  Returns `true` if `node` is a leaf. It is possible for this method to return `false` even if `node` 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.

  Parameters:
    `node` - a node in the tree, obtained from this data source
  Returns:
    true if `node` is a leaf

### valueForPathChanged

    public void valueForPathChanged(TreePath path,
                                    Object newValue)

  Messaged when the user has altered the value for the item identified by `path` to `newValue`. If `newValue` signifies a truly new value the model should post a `treeNodesChanged` event.

  Parameters:
    `path` - path to the node that the user has altered
    `newValue` - the new value from the TreeCellEditor

### getIndexOfChild

    public int getIndexOfChild(Object parent,
                               Object child)

  Returns the index of child in parent. If `parent` is `null` or `child` is `null`, returns -1.

  Parameters:
    `parent` - a note in the tree, obtained from this data source
    `child` - the node we are interested in
  Returns:
    the index of the child in the parent, or -1 if either `child` or `parent` are `null`

### addTreeModelListener

    public void addTreeModelListener(TreeModelListener l)

  Adds a listener for the `TreeModelEvent` posted after the tree changes.

  Parameters:
    `l` - the listener to add
  See Also:
    `removeTreeModelListener(javax.swing.event.TreeModelListener)`

### removeTreeModelListener

    public void removeTreeModelListener(TreeModelListener l)

  Removes a listener previously added with `addTreeModelListener`.

  Parameters:
    `l` - the listener to remove
  See Also:
    `addTreeModelListener(javax.swing.event.TreeModelListener)`

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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

Copyright 2003 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.