TreeModelEvent (Java Platform SE 8 )
Keywords: javax.swing.event.TreeModelEvent class
Date: 2026-01-21

javax.swing.event

## Class TreeModelEvent

- java.lang.Object
- - java.util.EventObject
  - - javax.swing.event.TreeModelEvent

- All Implemented Interfaces:
    Serializable

      public class TreeModelEvent
      extends EventObject

  Encapsulates information describing changes to a tree model, and used to notify tree model listeners of the change. For more information and examples see How to Write a Tree Model Listener, a section in The Java Tutorial.

  Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeans™ has been added to the `java.beans` package. Please see `XMLEncoder`.

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected int[]` | `childIndices` Indices identifying the position of where the children were.
    `protected Object[]` | `children` Children that have been removed.
    `protected TreePath` | `path` Path to the parent of the nodes that have changed.

    - ### Fields inherited from class java.util.EventObject

      `source`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `TreeModelEvent(Object source, Object[] path)` Used to create an event when the node structure has changed in some way, identifying the path to the root of a modified subtree as an array of Objects.
    `TreeModelEvent(Object source, Object[] path, int[] childIndices, Object[] children)` Used to create an event when nodes have been changed, inserted, or removed, identifying the path to the parent of the modified items as an array of Objects.
    `TreeModelEvent(Object source, TreePath path)` Used to create an event when the node structure has changed in some way, identifying the path to the root of the modified subtree as a TreePath object.
    `TreeModelEvent(Object source, TreePath path, int[] childIndices, Object[] children)` Used to create an event when nodes have been changed, inserted, or removed, identifying the path to the parent of the modified items as a TreePath object.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `int[]` | `getChildIndices()` Returns the values of the child indexes.
    `Object[]` | `getChildren()` Returns the objects that are children of the node identified by `getPath` at the locations specified by `getChildIndices`.
    `Object[]` | `getPath()` Convenience method to get the array of objects from the TreePath instance that this event wraps.
    `TreePath` | `getTreePath()` For all events, except treeStructureChanged, returns the parent of the changed nodes.
    `String` | `toString()` Returns a string that displays and identifies this object's properties.

    - ### Methods inherited from class java.util.EventObject

      `getSource`

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

- - ### Field Detail

    - #### path

          protected TreePath path

      Path to the parent of the nodes that have changed.

    - #### childIndices

          protected int[] childIndices

      Indices identifying the position of where the children were.

    - #### children

          protected Object[] children

      Children that have been removed.

  - ### Constructor Detail

    - #### TreeModelEvent

          public TreeModelEvent(Object source,
                                Object[] path,
                                int[] childIndices,
                                Object[] children)

      Used to create an event when nodes have been changed, inserted, or removed, identifying the path to the parent of the modified items as an array of Objects. All of the modified objects are siblings which are direct descendents (not grandchildren) of the specified parent. The positions at which the inserts, deletes, or changes occurred are specified by an array of `int`. The indexes in that array must be in order, from lowest to highest.

      For changes, the indexes in the model correspond exactly to the indexes of items currently displayed in the UI. As a result, it is not really critical if the indexes are not in their exact order. But after multiple inserts or deletes, the items currently in the UI no longer correspond to the items in the model. It is therefore critical to specify the indexes properly for inserts and deletes.

      For inserts, the indexes represent the final state of the tree, after the inserts have occurred. Since the indexes must be specified in order, the most natural processing methodology is to do the inserts starting at the lowest index and working towards the highest. Accumulate a Vector of `Integer` objects that specify the insert-locations as you go, then convert the Vector to an array of `int` to create the event. When the postition-index equals zero, the node is inserted at the beginning of the list. When the position index equals the size of the list, the node is "inserted" at (appended to) the end of the list.

      For deletes, the indexes represent the initial state of the tree, before the deletes have occurred. Since the indexes must be specified in order, the most natural processing methodology is to use a delete-counter. Start by initializing the counter to zero and start work through the list from lowest to highest. Every time you do a delete, add the current value of the delete-counter to the index-position where the delete occurred, and append the result to a Vector of delete-locations, using `addElement()`. Then increment the delete-counter. The index positions stored in the Vector therefore reflect the effects of all previous deletes, so they represent each object's position in the initial tree. (You could also start at the highest index and working back towards the lowest, accumulating a Vector of delete-locations as you go using the `insertElementAt(Integer, 0)`.) However you produce the Vector of initial-positions, you then need to convert the Vector of `Integer` objects to an array of `int` to create the event.

      Notes:

      - Like the `insertNodeInto` method in the `DefaultTreeModel` class, `insertElementAt` appends to the `Vector` when the index matches the size of the vector. So you can use `insertElementAt(Integer, 0)` even when the vector is empty.
      - To create a node changed event for the root node, specify the parent and the child indices as `null`.
      Parameters:
        `source` - the Object responsible for generating the event (typically the creator of the event object passes `this` for its value)
        `path` - an array of Object identifying the path to the parent of the modified item(s), where the first element of the array is the Object stored at the root node and the last element is the Object stored at the parent node
        `childIndices` - an array of `int` that specifies the index values of the removed items. The indices must be in sorted order, from lowest to highest
        `children` - an array of Object containing the inserted, removed, or changed objects
      See Also:
        `TreePath`

    - #### TreeModelEvent

          public TreeModelEvent(Object source,
                                TreePath path,
                                int[] childIndices,
                                Object[] children)

      Used to create an event when nodes have been changed, inserted, or removed, identifying the path to the parent of the modified items as a TreePath object. For more information on how to specify the indexes and objects, see `TreeModelEvent(Object,Object[],int[],Object[])`.
      Parameters:
        `source` - the Object responsible for generating the event (typically the creator of the event object passes `this` for its value)
        `path` - a TreePath object that identifies the path to the parent of the modified item(s)
        `childIndices` - an array of `int` that specifies the index values of the modified items
        `children` - an array of Object containing the inserted, removed, or changed objects
      See Also:
        `TreeModelEvent(Object,Object[],int[],Object[])`

    - #### TreeModelEvent

          public TreeModelEvent(Object source,
                                Object[] path)

      Used to create an event when the node structure has changed in some way, identifying the path to the root of a modified subtree as an array of Objects. A structure change event might involve nodes swapping position, for example, or it might encapsulate multiple inserts and deletes in the subtree stemming from the node, where the changes may have taken place at different levels of the subtree.

      > Note:
      > JTree collapses all nodes under the specified node, so that only its immediate children are visible.

      Parameters:
        `source` - the Object responsible for generating the event (typically the creator of the event object passes `this` for its value)
        `path` - an array of Object identifying the path to the root of the modified subtree, where the first element of the array is the object stored at the root node and the last element is the object stored at the changed node
      See Also:
        `TreePath`

    - #### TreeModelEvent

          public TreeModelEvent(Object source,
                                TreePath path)

      Used to create an event when the node structure has changed in some way, identifying the path to the root of the modified subtree as a TreePath object. For more information on this event specification, see `TreeModelEvent(Object,Object[])`.
      Parameters:
        `source` - the Object responsible for generating the event (typically the creator of the event object passes `this` for its value)
        `path` - a TreePath object that identifies the path to the change. In the DefaultTreeModel, this object contains an array of user-data objects, but a subclass of TreePath could use some totally different mechanism -- for example, a node ID number
      See Also:
        `TreeModelEvent(Object,Object[])`

  - ### Method Detail

    - #### getTreePath

          public TreePath getTreePath()

      For all events, except treeStructureChanged, returns the parent of the changed nodes. For treeStructureChanged events, returns the ancestor of the structure that has changed. This and `getChildIndices` are used to get a list of the effected nodes.

      The one exception to this is a treeNodesChanged event that is to identify the root, in which case this will return the root and `getChildIndices` will return null.

      Returns:
        the TreePath used in identifying the changed nodes.
      See Also:
        `TreePath.getLastPathComponent()`

    - #### getPath

          public Object[] getPath()

      Convenience method to get the array of objects from the TreePath instance that this event wraps.
      Returns:
        an array of Objects, where the first Object is the one stored at the root and the last object is the one stored at the node identified by the path

    - #### getChildren

          public Object[] getChildren()

      Returns the objects that are children of the node identified by `getPath` at the locations specified by `getChildIndices`. If this is a removal event the returned objects are no longer children of the parent node.
      Returns:
        an array of Object containing the children specified by the event
      See Also:
        `getPath()`, `getChildIndices()`

    - #### getChildIndices

          public int[] getChildIndices()

      Returns the values of the child indexes. If this is a removal event the indexes point to locations in the initial list where items were removed. If it is an insert, the indices point to locations in the final list where the items were added. For node changes, the indices point to the locations of the modified nodes.
      Returns:
        an array of `int` containing index locations for the children specified by the event

    - #### toString

          public String toString()

      Returns a string that displays and identifies this object's properties.
      Overrides:
        `toString` in class `EventObject`
      Returns:
        a String representation of this object

Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
Copyright © 1993, 2026, Oracle and/or its affiliates. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.