DefaultMutableTreeNode (Java 2 Platform SE 5.0) - JDK 5 Documentation v1.5.0, Java 2 SDK 英文文档

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Java^TM 2 Platform
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javax.swing.tree
Class DefaultMutableTreeNode

java.lang.Object
  javax.swing.tree.DefaultMutableTreeNode

All Implemented Interfaces:: Serializable, Cloneable, MutableTreeNode, TreeNode

Direct Known Subclasses:: JTree.DynamicUtilTreeNode

public class DefaultMutableTreeNode
extends Object
implements Cloneable, MutableTreeNode, Serializable
extends Object
implements Cloneable, MutableTreeNode, Serializable

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 JavaBeans^TM has been added to the java.beans package. Please see XMLEncoder.

See Also:: MutableTreeNode

Field Summary

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

static Enumeration<TreeNode> EMPTY_ENUMERATION
          An enumeration that is always empty.

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

protected Object userObject
          optional user object

Constructor Summary

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.

Method Summary

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.

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.

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.

Methods inherited from class java.lang.Object

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

Field Summary
`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
`static Enumeration<TreeNode>`	`EMPTY_ENUMERATION` An enumeration that is always empty.
`protected MutableTreeNode`	`parent` this node's parent, or null if this node has no parent
`protected Object`	`userObject` optional user object

Constructor Summary
`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.

Method Summary
`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.
`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.
`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.

Methods inherited from class java.lang.Object
`equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Field Detail

EMPTY_ENUMERATION

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.

parent

protected MutableTreeNode parent

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

children

protected Vector children

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

userObject

protected transient Object userObject

optional user object

allowsChildren

protected boolean allowsChildren

true if the node is able to have children

Constructor Detail

DefaultMutableTreeNode

public DefaultMutableTreeNode()

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

DefaultMutableTreeNode

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

DefaultMutableTreeNode

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

Method Detail

insert

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.

Specified by:: insert in interface MutableTreeNode

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:: isNodeDescendant(javax.swing.tree.DefaultMutableTreeNode)

remove

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.

Specified by:: remove in interface MutableTreeNode

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

setParent

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.

Specified by:: setParent in interface MutableTreeNode

Parameters:: newParent - this node's new parent

getParent

public TreeNode getParent()

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

Specified by:: getParent in interface TreeNode

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

getChildAt

public TreeNode getChildAt(int index)

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

Specified by:: getChildAt in interface TreeNode

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

getChildCount

public int getChildCount()

Returns the number of children of this node.

Specified by:: getChildCount in interface TreeNode

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

getIndex

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.

Specified by:: getIndex in interface TreeNode

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

children

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.

Specified by:: children in interface TreeNode

Returns:: an Enumeration of this node's children

setAllowsChildren

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

getAllowsChildren

public boolean getAllowsChildren()

Returns true if this node is allowed to have children.

Specified by:: getAllowsChildren in interface TreeNode

Returns:: true if this node allows children, else false

setUserObject

public void setUserObject(Object userObject)

Sets the user object for this node to userObject.

Specified by:: setUserObject in interface MutableTreeNode

Parameters:: userObject - the Object that constitutes this node's user-specified data
See Also:: getUserObject(), toString()

getUserObject

public Object getUserObject()

Returns this node's user object.

Returns:: the Object stored at this node by the user
See Also:: setUserObject(java.lang.Object), toString()

removeFromParent

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.

Specified by:: removeFromParent in interface MutableTreeNode

remove

public void remove(MutableTreeNode aChild)

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

Specified by:: remove in interface MutableTreeNode

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

removeAllChildren

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.

add

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:: insert(javax.swing.tree.MutableTreeNode, int)

isNodeAncestor

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:: isNodeDescendant(javax.swing.tree.DefaultMutableTreeNode), getSharedAncestor(javax.swing.tree.DefaultMutableTreeNode)

isNodeDescendant

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:: isNodeAncestor(javax.swing.tree.TreeNode), getSharedAncestor(javax.swing.tree.DefaultMutableTreeNode)

getSharedAncestor

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:: isNodeAncestor(javax.swing.tree.TreeNode), isNodeDescendant(javax.swing.tree.DefaultMutableTreeNode)

isNodeRelated

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:: getSharedAncestor(javax.swing.tree.DefaultMutableTreeNode), getRoot()

getDepth

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:: getLevel()

getLevel

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:: getDepth()

getPath

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.

getPathToRoot

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

getUserObjectPath

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.

getRoot

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:: isNodeAncestor(javax.swing.tree.TreeNode)

isRoot

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

getNextNode

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:: preorderEnumeration()

getPreviousNode

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:: preorderEnumeration()

preorderEnumeration

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.