public class

DefaultMutableTreeNode

extends Object
implements Serializable Cloneable MutableTreeNode
java.lang.Object
   ↳ javax.swing.tree.DefaultMutableTreeNode
Known Direct Subclasses

Class Overview

A DefaultMutableTreeNode is a general-purpose node in a tree data structure. For examples of using default mutable tree nodes, see How to Use Trees in The Java Tutorial.

A tree node may have at most one parent and 0 or more children. DefaultMutableTreeNode provides operations for examining and modifying a node's parent and children and also operations for examining the tree that the node is a part of. A node's tree is the set of all nodes that can be reached by starting at the node and following all the possible links to parents and children. A node with no parent is the root of its tree; a node with no children is a leaf. A tree may consist of many subtrees, each node acting as the root for its own subtree.

This class provides enumerations for efficiently traversing a tree or subtree in various orders or for following the path between two nodes. A DefaultMutableTreeNode may also hold a reference to a user object, the use of which is left to the user. Asking a DefaultMutableTreeNode for its string representation with toString() returns the string representation of its user object.

This is not a thread safe class.If you intend to use a DefaultMutableTreeNode (or a tree of TreeNodes) in more than one thread, you need to do your own synchronizing. A good convention to adopt is synchronizing on the root node of a tree.

While DefaultMutableTreeNode implements the MutableTreeNode interface and will allow you to add in any implementation of MutableTreeNode not all of the methods in DefaultMutableTreeNode will be applicable to all MutableTreeNodes implementations. Especially with some of the enumerations that are provided, using some of these methods assumes the DefaultMutableTreeNode contains only DefaultMutableNode instances. All of the TreeNode/MutableTreeNode methods will behave as defined no matter what implementations are added.

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 JavaBeansTM has been added to the java.beans package. Please see XMLEncoder.

See Also

Summary

Fields
public static final Enumeration<TreeNode> EMPTY_ENUMERATION An enumeration that is always empty.
protected boolean allowsChildren true if the node is able to have children
protected Vector children array of children, may be null if this node has no children
protected MutableTreeNode parent this node's parent, or null if this node has no parent
protected Object userObject optional user object
Public Constructors
DefaultMutableTreeNode()
Creates a tree node that has no parent and no children, but which allows children.
DefaultMutableTreeNode(Object userObject)
Creates a tree node with no parent, no children, but which allows children, and initializes it with the specified user object.
DefaultMutableTreeNode(Object userObject, boolean allowsChildren)
Creates a tree node with no parent, no children, initialized with the specified user object, and that allows children only if specified.
Public Methods
void add(MutableTreeNode newChild)
Removes newChild from its parent and makes it a child of this node by adding it to the end of this node's child array.
Enumeration breadthFirstEnumeration()
Creates and returns an enumeration that traverses the subtree rooted at this node in breadth-first order.
Enumeration children()
Creates and returns a forward-order enumeration of this node's children.
Object clone()
Overridden to make clone public.
Enumeration depthFirstEnumeration()
Creates and returns an enumeration that traverses the subtree rooted at this node in depth-first order.
boolean getAllowsChildren()
Returns true if this node is allowed to have children.
TreeNode getChildAfter(TreeNode aChild)
Returns the child in this node's child array that immediately follows aChild, which must be a child of this node.
TreeNode getChildAt(int index)
Returns the child at the specified index in this node's child array.
TreeNode getChildBefore(TreeNode aChild)
Returns the child in this node's child array that immediately precedes aChild, which must be a child of this node.
int getChildCount()
Returns the number of children of this node.
int getDepth()
Returns the depth of the tree rooted at this node -- the longest distance from this node to a leaf.
TreeNode getFirstChild()
Returns this node's first child.
DefaultMutableTreeNode getFirstLeaf()
Finds and returns the first leaf that is a descendant of this node -- either this node or its first child's first leaf.
int getIndex(TreeNode aChild)
Returns the index of the specified child in this node's child array.
TreeNode getLastChild()
Returns this node's last child.
DefaultMutableTreeNode getLastLeaf()
Finds and returns the last leaf that is a descendant of this node -- either this node or its last child's last leaf.
int getLeafCount()
Returns the total number of leaves that are descendants of this node.
int getLevel()
Returns the number of levels above this node -- the distance from the root to this node.
DefaultMutableTreeNode getNextLeaf()
Returns the leaf after this node or null if this node is the last leaf in the tree.
DefaultMutableTreeNode getNextNode()
Returns the node that follows this node in a preorder traversal of this node's tree.
DefaultMutableTreeNode getNextSibling()
Returns the next sibling of this node in the parent's children array.
TreeNode getParent()
Returns this node's parent or null if this node has no parent.
TreeNode[] getPath()
Returns the path from the root, to get to this node.
DefaultMutableTreeNode getPreviousLeaf()
Returns the leaf before this node or null if this node is the first leaf in the tree.
DefaultMutableTreeNode getPreviousNode()
Returns the node that precedes this node in a preorder traversal of this node's tree.
DefaultMutableTreeNode getPreviousSibling()
Returns the previous sibling of this node in the parent's children array.
TreeNode getRoot()
Returns the root of the tree that contains this node.
TreeNode getSharedAncestor(DefaultMutableTreeNode aNode)
Returns the nearest common ancestor to this node and aNode.
int getSiblingCount()
Returns the number of siblings of this node.
Object getUserObject()
Returns this node's user object.
Object[] getUserObjectPath()
Returns the user object path, from the root, to get to this node.
void insert(MutableTreeNode newChild, int childIndex)
Removes newChild from its present parent (if it has a parent), sets the child's parent to this node, and then adds the child to this node's child array at index childIndex.
boolean isLeaf()
Returns true if this node has no children.
boolean isNodeAncestor(TreeNode anotherNode)
Returns true if anotherNode is an ancestor of this node -- if it is this node, this node's parent, or an ancestor of this node's parent.
boolean isNodeChild(TreeNode aNode)
Returns true if aNode is a child of this node.
boolean isNodeDescendant(DefaultMutableTreeNode anotherNode)
Returns true if anotherNode is a descendant of this node -- if it is this node, one of this node's children, or a descendant of one of this node's children.
boolean isNodeRelated(DefaultMutableTreeNode aNode)
Returns true if and only if aNode is in the same tree as this node.
boolean isNodeSibling(TreeNode anotherNode)
Returns true if anotherNode is a sibling of (has the same parent as) this node.
boolean isRoot()
Returns true if this node is the root of the tree.
Enumeration pathFromAncestorEnumeration(TreeNode ancestor)
Creates and returns an enumeration that follows the path from ancestor to this node.
Enumeration postorderEnumeration()
Creates and returns an enumeration that traverses the subtree rooted at this node in postorder.
Enumeration preorderEnumeration()
Creates and returns an enumeration that traverses the subtree rooted at this node in preorder.
void remove(int childIndex)
Removes the child at the specified index from this node's children and sets that node's parent to null.
void remove(MutableTreeNode aChild)
Removes aChild from this node's child array, giving it a null parent.
void removeAllChildren()
Removes all of this node's children, setting their parents to null.
void removeFromParent()
Removes the subtree rooted at this node from the tree, giving this node a null parent.
void setAllowsChildren(boolean allows)
Determines whether or not this node is allowed to have children.
void setParent(MutableTreeNode newParent)
Sets this node's parent to newParent but does not change the parent's child array.
void setUserObject(Object userObject)
Sets the user object for this node to userObject.
String toString()
Returns the result of sending toString() to this node's user object, or null if this node has no user object.
Protected Methods
TreeNode[] getPathToRoot(TreeNode aNode, int depth)
Builds the parents of node up to and including the root node, where the original node is the last element in the returned array.
[Expand]
Inherited Methods
From class java.lang.Object
From interface javax.swing.tree.MutableTreeNode
From interface javax.swing.tree.TreeNode

Fields

public static final Enumeration<TreeNode> EMPTY_ENUMERATION

An enumeration that is always empty. This is used when an enumeration of a leaf node's children is requested.

protected boolean allowsChildren

true if the node is able to have children

protected Vector children

array of children, may be null if this node has no children

protected MutableTreeNode parent

this node's parent, or null if this node has no parent

protected Object userObject

optional user object

Public Constructors

public DefaultMutableTreeNode ()

Creates a tree node that has no parent and no children, but which allows children.

public DefaultMutableTreeNode (Object userObject)

Creates a tree node with no parent, no children, but which allows children, and initializes it with the specified user object.

Parameters
userObject an Object provided by the user that constitutes the node's data

public DefaultMutableTreeNode (Object userObject, boolean allowsChildren)

Creates a tree node with no parent, no children, initialized with the specified user object, and that allows children only if specified.

Parameters
userObject an Object provided by the user that constitutes the node's data
allowsChildren if true, the node is allowed to have child nodes -- otherwise, it is always a leaf node

Public Methods

public void add (MutableTreeNode newChild)

Removes newChild from its parent and makes it a child of this node by adding it to the end of this node's child array.

Parameters
newChild node to add as a child of this node
Throws
IllegalArgumentException if newChild is null
IllegalStateException if this node does not allow children
See Also

public Enumeration breadthFirstEnumeration ()

Creates and returns an enumeration that traverses the subtree rooted at this node in breadth-first order. The first node returned by the enumeration's nextElement() method is this node.

Modifying the tree by inserting, removing, or moving a node invalidates any enumerations created before the modification.

Returns
  • an enumeration for traversing the tree in breadth-first order
See Also

public Enumeration children ()

Creates and returns a forward-order enumeration of this node's children. Modifying this node's child array invalidates any child enumerations created before the modification.

Returns
  • an Enumeration of this node's children

public Object clone ()

Overridden to make clone public. Returns a shallow copy of this node; the new node has no parent or children and has a reference to the same user object, if any.

Returns
  • a copy of this node

public Enumeration depthFirstEnumeration ()

Creates and returns an enumeration that traverses the subtree rooted at this node in depth-first order. The first node returned by the enumeration's nextElement() method is the leftmost leaf. This is the same as a postorder traversal.

Modifying the tree by inserting, removing, or moving a node invalidates any enumerations created before the modification.

Returns
  • an enumeration for traversing the tree in depth-first order
See Also

public boolean getAllowsChildren ()

Returns true if this node is allowed to have children.

Returns
  • true if this node allows children, else false

public TreeNode getChildAfter (TreeNode aChild)

Returns the child in this node's child array that immediately follows aChild, which must be a child of this node. If aChild is the last child, returns null. This method performs a linear search of this node's children for aChild and is O(n) where n is the number of children; to traverse the entire array of children, use an enumeration instead.

Returns
  • the child of this node that immediately follows aChild
Throws
IllegalArgumentException if aChild is null or is not a child of this node
See Also

public TreeNode getChildAt (int index)

Returns the child at the specified index in this node's child array.

Parameters
index an index into this node's child array
Returns
  • the TreeNode in this node's child array at the specified index
Throws
ArrayIndexOutOfBoundsException if index is out of bounds

public TreeNode getChildBefore (TreeNode aChild)

Returns the child in this node's child array that immediately precedes aChild, which must be a child of this node. If aChild is the first child, returns null. This method performs a linear search of this node's children for aChild and is O(n) where n is the number of children.

Returns
  • the child of this node that immediately precedes aChild
Throws
IllegalArgumentException if aChild is null or is not a child of this node

public int getChildCount ()

Returns the number of children of this node.

Returns
  • an int giving the number of children of this node

public int getDepth ()

Returns the depth of the tree rooted at this node -- the longest distance from this node to a leaf. If this node has no children, returns 0. This operation is much more expensive than getLevel() because it must effectively traverse the entire tree rooted at this node.

Returns
  • the depth of the tree whose root is this node
See Also

public TreeNode getFirstChild ()

Returns this node's first child. If this node has no children, throws NoSuchElementException.

Returns
  • the first child of this node
Throws
NoSuchElementException if this node has no children

public DefaultMutableTreeNode getFirstLeaf ()

Finds and returns the first leaf that is a descendant of this node -- either this node or its first child's first leaf. Returns this node if it is a leaf.

Returns
  • the first leaf in the subtree rooted at this node
See Also

public int getIndex (TreeNode aChild)

Returns the index of the specified child in this node's child array. If the specified node is not a child of this node, returns -1. This method performs a linear search and is O(n) where n is the number of children.

Parameters
aChild the TreeNode to search for among this node's children
Returns
  • an int giving the index of the node in this node's child array, or -1 if the specified node is a not a child of this node
Throws
IllegalArgumentException if aChild is null

public TreeNode getLastChild ()

Returns this node's last child. If this node has no children, throws NoSuchElementException.

Returns
  • the last child of this node
Throws
NoSuchElementException if this node has no children

public DefaultMutableTreeNode getLastLeaf ()

Finds and returns the last leaf that is a descendant of this node -- either this node or its last child's last leaf. Returns this node if it is a leaf.

Returns
  • the last leaf in the subtree rooted at this node
See Also

public int getLeafCount ()

Returns the total number of leaves that are descendants of this node. If this node is a leaf, returns 1. This method is O(n) where n is the number of descendants of this node.

Returns
  • the number of leaves beneath this node
See Also

public int getLevel ()

Returns the number of levels above this node -- the distance from the root to this node. If this node is the root, returns 0.

Returns
  • the number of levels above this node
See Also

public DefaultMutableTreeNode getNextLeaf ()

Returns the leaf after this node or null if this node is the last leaf in the tree.

In this implementation of the MutableNode interface, this operation is very inefficient. In order to determine the next node, this method first performs a linear search in the parent's child-list in order to find the current node.

That implementation makes the operation suitable for short traversals from a known position. But to traverse all of the leaves in the tree, you should use depthFirstEnumeration to enumerate the nodes in the tree and use isLeaf on each node to determine which are leaves.

Returns
  • returns the next leaf past this node
See Also

public DefaultMutableTreeNode getNextNode ()

Returns the node that follows this node in a preorder traversal of this node's tree. Returns null if this node is the last node of the traversal. This is an inefficient way to traverse the entire tree; use an enumeration, instead.

Returns
  • the node that follows this node in a preorder traversal, or null if this node is last
See Also

public DefaultMutableTreeNode getNextSibling ()

Returns the next sibling of this node in the parent's children array. Returns null if this node has no parent or is the parent's last child. This method performs a linear search that is O(n) where n is the number of children; to traverse the entire array, use the parent's child enumeration instead.

Returns
  • the sibling of this node that immediately follows this node
See Also

public TreeNode getParent ()

Returns this node's parent or null if this node has no parent.

Returns
  • this node's parent TreeNode, or null if this node has no parent

public TreeNode[] getPath ()

Returns the path from the root, to get to this node. The last element in the path is this node.

Returns
  • an array of TreeNode objects giving the path, where the first element in the path is the root and the last element is this node.

public DefaultMutableTreeNode getPreviousLeaf ()

Returns the leaf before this node or null if this node is the first leaf in the tree.

In this implementation of the MutableNode interface, this operation is very inefficient. In order to determine the previous node, this method first performs a linear search in the parent's child-list in order to find the current node.

That implementation makes the operation suitable for short traversals from a known position. But to traverse all of the leaves in the tree, you should use depthFirstEnumeration to enumerate the nodes in the tree and use isLeaf on each node to determine which are leaves.

Returns
  • returns the leaf before this node
See Also

public DefaultMutableTreeNode getPreviousNode ()

Returns the node that precedes this node in a preorder traversal of this node's tree. Returns null if this node is the first node of the traversal -- the root of the tree. This is an inefficient way to traverse the entire tree; use an enumeration, instead.

Returns
  • the node that precedes this node in a preorder traversal, or null if this node is the first
See Also

public DefaultMutableTreeNode getPreviousSibling ()

Returns the previous sibling of this node in the parent's children array. Returns null if this node has no parent or is the parent's first child. This method performs a linear search that is O(n) where n is the number of children.

Returns
  • the sibling of this node that immediately precedes this node

public TreeNode getRoot ()

Returns the root of the tree that contains this node. The root is the ancestor with a null parent.

Returns
  • the root of the tree that contains this node
See Also

public TreeNode getSharedAncestor (DefaultMutableTreeNode aNode)

Returns the nearest common ancestor to this node and aNode. Returns null, if no such ancestor exists -- if this node and aNode are in different trees or if aNode is null. A node is considered an ancestor of itself.

Parameters
aNode node to find common ancestor with
Returns
  • nearest ancestor common to this node and aNode, or null if none
See Also

public int getSiblingCount ()

Returns the number of siblings of this node. A node is its own sibling (if it has no parent or no siblings, this method returns 1).

Returns
  • the number of siblings of this node

public Object getUserObject ()

Returns this node's user object.

Returns
  • the Object stored at this node by the user
See Also

public Object[] getUserObjectPath ()

Returns the user object path, from the root, to get to this node. If some of the TreeNodes in the path have null user objects, the returned path will contain nulls.

public void insert (MutableTreeNode newChild, int childIndex)

Removes newChild from its present parent (if it has a parent), sets the child's parent to this node, and then adds the child to this node's child array at index childIndex. newChild must not be null and must not be an ancestor of this node.

Parameters
newChild the MutableTreeNode to insert under this node
childIndex the index in this node's child array where this node is to be inserted
Throws
ArrayIndexOutOfBoundsException if childIndex is out of bounds
IllegalArgumentException if newChild is null or is an ancestor of this node
IllegalStateException if this node does not allow children
See Also

public boolean isLeaf ()

Returns true if this node has no children. To distinguish between nodes that have no children and nodes that cannot have children (e.g. to distinguish files from empty directories), use this method in conjunction with getAllowsChildren

Returns
  • true if this node has no children
See Also

public boolean isNodeAncestor (TreeNode anotherNode)

Returns true if anotherNode is an ancestor of this node -- if it is this node, this node's parent, or an ancestor of this node's parent. (Note that a node is considered an ancestor of itself.) If anotherNode is null, this method returns false. This operation is at worst O(h) where h is the distance from the root to this node.

Parameters
anotherNode node to test as an ancestor of this node
Returns
  • true if this node is a descendant of anotherNode
See Also

public boolean isNodeChild (TreeNode aNode)

Returns true if aNode is a child of this node. If aNode is null, this method returns false.

Returns
  • true if aNode is a child of this node; false if aNode is null

public boolean isNodeDescendant (DefaultMutableTreeNode anotherNode)

Returns true if anotherNode is a descendant of this node -- if it is this node, one of this node's children, or a descendant of one of this node's children. Note that a node is considered a descendant of itself. If anotherNode is null, returns false. This operation is at worst O(h) where h is the distance from the root to anotherNode.

Parameters
anotherNode node to test as descendant of this node
Returns
  • true if this node is an ancestor of anotherNode
See Also

public boolean isNodeRelated (DefaultMutableTreeNode aNode)

Returns true if and only if aNode is in the same tree as this node. Returns false if aNode is null.

Returns
  • true if aNode is in the same tree as this node; false if aNode is null
See Also

public boolean isNodeSibling (TreeNode anotherNode)

Returns true if anotherNode is a sibling of (has the same parent as) this node. A node is its own sibling. If anotherNode is null, returns false.

Parameters
anotherNode node to test as sibling of this node
Returns
  • true if anotherNode is a sibling of this node

public boolean isRoot ()

Returns true if this node is the root of the tree. The root is the only node in the tree with a null parent; every tree has exactly one root.

Returns
  • true if this node is the root of its tree

public Enumeration pathFromAncestorEnumeration (TreeNode ancestor)

Creates and returns an enumeration that follows the path from ancestor to this node. The enumeration's nextElement() method first returns ancestor, then the child of ancestor that is an ancestor of this node, and so on, and finally returns this node. Creation of the enumeration is O(m) where m is the number of nodes between this node and ancestor, inclusive. Each nextElement() message is O(1).

Modifying the tree by inserting, removing, or moving a node invalidates any enumerations created before the modification.

Returns
  • an enumeration for following the path from an ancestor of this node to this one
Throws
IllegalArgumentException if ancestor is not an ancestor of this node
See Also

public Enumeration postorderEnumeration ()

Creates and returns an enumeration that traverses the subtree rooted at this node in postorder. The first node returned by the enumeration's nextElement() method is the leftmost leaf. This is the same as a depth-first traversal.

Modifying the tree by inserting, removing, or moving a node invalidates any enumerations created before the modification.

Returns
  • an enumeration for traversing the tree in postorder
See Also

public Enumeration preorderEnumeration ()

Creates and returns an enumeration that traverses the subtree rooted at this node in preorder. The first node returned by the enumeration's nextElement() method is this node.

Modifying the tree by inserting, removing, or moving a node invalidates any enumerations created before the modification.

Returns
  • an enumeration for traversing the tree in preorder
See Also

public void remove (int childIndex)

Removes the child at the specified index from this node's children and sets that node's parent to null. The child node to remove must be a MutableTreeNode.

Parameters
childIndex the index in this node's child array of the child to remove
Throws
ArrayIndexOutOfBoundsException if childIndex is out of bounds

public void remove (MutableTreeNode aChild)

Removes aChild from this node's child array, giving it a null parent.

Parameters
aChild a child of this node to remove
Throws
IllegalArgumentException if aChild is null or is not a child of this node

public void removeAllChildren ()

Removes all of this node's children, setting their parents to null. If this node has no children, this method does nothing.

public void removeFromParent ()

Removes the subtree rooted at this node from the tree, giving this node a null parent. Does nothing if this node is the root of its tree.

public void setAllowsChildren (boolean allows)

Determines whether or not this node is allowed to have children. If allows is false, all of this node's children are removed.

Note: By default, a node allows children.

Parameters
allows true if this node is allowed to have children

public void setParent (MutableTreeNode newParent)

Sets this node's parent to newParent but does not change the parent's child array. This method is called from insert() and remove() to reassign a child's parent, it should not be messaged from anywhere else.

Parameters
newParent this node's new parent

public void setUserObject (Object userObject)

Sets the user object for this node to userObject.

Parameters
userObject the Object that constitutes this node's user-specified data
See Also

public String toString ()

Returns the result of sending toString() to this node's user object, or null if this node has no user object.

Returns
  • a string representation of the object.
See Also

Protected Methods

protected TreeNode[] getPathToRoot (TreeNode aNode, int depth)

Builds the parents of node up to and including the root node, where the original node is the last element in the returned array. The length of the returned array gives the node's depth in the tree.

Parameters
aNode the TreeNode to get the path for
depth an int giving the number of steps already taken towards the root (on recursive calls), used to size the returned array
Returns
  • an array of TreeNodes giving the path from the root to the specified node