public class DefaultMutableTreeNode 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™ has been added to the java.beans
package. Please see XMLEncoder
.
MutableTreeNode
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 MutableTreeNode parent
this node's parent, or null if this node has no parent
protected Vector children
array of children, may be null if this node has no children
protected transient Object userObject
optional user object
protected boolean allowsChildren
true if the node is able to have children
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.
userObject
- an Object provided by the user that constitutes the node's datapublic 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.
userObject
- an Object provided by the user that constitutes the node's dataallowsChildren
- if true, the node is allowed to have child nodes -- otherwise, it is always a leaf nodepublic 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.
insert
in interface MutableTreeNode
newChild
- the MutableTreeNode to insert under this nodechildIndex
- the index in this node's child array where this node is to be insertedArrayIndexOutOfBoundsException
- if childIndex
is out of boundsIllegalArgumentException
- if newChild
is null or is an ancestor of this nodeIllegalStateException
- if this node does not allow childrenisNodeDescendant(javax.swing.tree.DefaultMutableTreeNode)
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
.
remove
in interface MutableTreeNode
childIndex
- the index in this node's child array of the child to removeArrayIndexOutOfBoundsException
- if childIndex
is out of boundspublic 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.
setParent
in interface MutableTreeNode
newParent
- this node's new parentpublic TreeNode getParent()
Returns this node's parent or null if this node has no parent.
getParent
in interface TreeNode
public TreeNode getChildAt(int index)
Returns the child at the specified index in this node's child array.
getChildAt
in interface TreeNode
index
- an index into this node's child arrayArrayIndexOutOfBoundsException
- if index
is out of boundspublic int getChildCount()
Returns the number of children of this node.
getChildCount
in interface TreeNode
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.
getIndex
in interface TreeNode
aChild
- the TreeNode to search for among this node's children-1
if the specified node is a not a child of this nodeIllegalArgumentException
- if aChild
is nullpublic 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.
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.
allows
- true if this node is allowed to have childrenpublic boolean getAllowsChildren()
Returns true if this node is allowed to have children.
getAllowsChildren
in interface TreeNode
public void setUserObject(Object userObject)
Sets the user object for this node to userObject
.
setUserObject
in interface MutableTreeNode
userObject
- the Object that constitutes this node's user-specified datagetUserObject()
, toString()
public Object getUserObject()
Returns this node's user object.
setUserObject(java.lang.Object)
, toString()
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.
removeFromParent
in interface MutableTreeNode
public void remove(MutableTreeNode aChild)
Removes aChild
from this node's child array, giving it a null parent.
remove
in interface MutableTreeNode
aChild
- a child of this node to removeIllegalArgumentException
- if aChild
is null or is not a child of this nodepublic 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 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.
newChild
- node to add as a child of this nodeIllegalArgumentException
- if newChild
is nullIllegalStateException
- if this node does not allow childreninsert(javax.swing.tree.MutableTreeNode, int)
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.
anotherNode
- node to test as an ancestor of this nodeanotherNode
isNodeDescendant(javax.swing.tree.DefaultMutableTreeNode)
, getSharedAncestor(javax.swing.tree.DefaultMutableTreeNode)
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
.
anotherNode
- node to test as descendant of this nodeanotherNode
isNodeAncestor(javax.swing.tree.TreeNode)
, getSharedAncestor(javax.swing.tree.DefaultMutableTreeNode)
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.
aNode
- node to find common ancestor withaNode
, or null if noneisNodeAncestor(javax.swing.tree.TreeNode)
, isNodeDescendant(javax.swing.tree.DefaultMutableTreeNode)
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.
aNode
is in the same tree as this node; false if aNode
is nullgetSharedAncestor(javax.swing.tree.DefaultMutableTreeNode)
, getRoot()
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.
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.
getDepth()
public TreeNode[] getPath()
Returns the path from the root, to get to this node. The last element in the path is 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. The length of the returned array gives the node's depth in the tree.
aNode
- the TreeNode to get the path fordepth
- an int giving the number of steps already taken towards the root (on recursive calls), used to size the returned arraypublic 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 TreeNode getRoot()
Returns the root of the tree that contains this node. The root is the ancestor with a null parent.
isNodeAncestor(javax.swing.tree.TreeNode)
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.
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.
preorderEnumeration()
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.
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.
Modifying the tree by inserting, removing, or moving a node invalidates any enumerations created before the modification.
postorderEnumeration()
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.
depthFirstEnumeration()
, preorderEnumeration()
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.
depthFirstEnumeration()
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.
breadthFirstEnumeration()
, postorderEnumeration()
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.
IllegalArgumentException
- if ancestor
is not an ancestor of this nodeisNodeAncestor(javax.swing.tree.TreeNode)
, isNodeDescendant(javax.swing.tree.DefaultMutableTreeNode)
public boolean isNodeChild(TreeNode aNode)
Returns true if aNode
is a child of this node. If aNode
is null, this method returns false.
aNode
is a child of this node; false if aNode
is nullpublic TreeNode getFirstChild()
Returns this node's first child. If this node has no children, throws NoSuchElementException.
NoSuchElementException
- if this node has no childrenpublic TreeNode getLastChild()
Returns this node's last child. If this node has no children, throws NoSuchElementException.
NoSuchElementException
- if this node has no childrenpublic 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.
aChild
IllegalArgumentException
- if aChild
is null or is not a child of this nodechildren
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.
aChild
IllegalArgumentException
- if aChild
is null or is not a child of this nodepublic 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.
anotherNode
- node to test as sibling of this nodeanotherNode
is a sibling of this nodepublic 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
).
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.
children
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.
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
isLeaf
in interface TreeNode
getAllowsChildren()
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.
isLeaf()
, isNodeDescendant(javax.swing.tree.DefaultMutableTreeNode)
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.
isLeaf()
, isNodeDescendant(javax.swing.tree.DefaultMutableTreeNode)
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.
depthFirstEnumeration()
, isLeaf()
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.
depthFirstEnumeration()
, isLeaf()
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.
isNodeAncestor(javax.swing.tree.TreeNode)
public String toString()
Returns the result of sending toString()
to this node's user object, or the empty string if the node has no user object.
toString
in class Object
getUserObject()
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.
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