The DefaultMutableTreeNode.java Java example source code
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* accompanied this code).
*
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package javax.swing.tree;
// ISSUE: this class depends on nothing in AWT -- move to java.util?
import java.beans.Transient;
import java.io.*;
import java.util.*;
/**
* A <code>DefaultMutableTreeNode is a general-purpose node in a tree data
* structure.
* For examples of using default mutable tree nodes, see
* <a
href="http://docs.oracle.com/javase/tutorial/uiswing/components/tree.html">How to Use Trees</a>
* in <em>The Java Tutorial.
*
* <p>
*
* A tree node may have at most one parent and 0 or more children.
* <code>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.
* <p>
* This class provides enumerations for efficiently traversing a tree or
* subtree in various orders or for following the path between two nodes.
* A <code>DefaultMutableTreeNode may also hold a reference to a user object, the
* use of which is left to the user. Asking a <code>DefaultMutableTreeNode for its
* string representation with <code>toString() returns the string
* representation of its user object.
* <p>
* <b>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.
* <p>
* 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.
*
* <p>
* <strong>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 <code>java.beans package.
* Please see {@link java.beans.XMLEncoder}.
*
* @see MutableTreeNode
*
* @author Rob Davis
*/
public class DefaultMutableTreeNode implements Cloneable,
MutableTreeNode, Serializable
{
private static final long serialVersionUID = -4298474751201349152L;
/**
* An enumeration that is always empty. This is used when an enumeration
* of a leaf node's children is requested.
*/
static public final Enumeration<TreeNode> EMPTY_ENUMERATION
= Collections.emptyEnumeration();
/** this node's parent, or null if this node has no parent */
protected MutableTreeNode parent;
/** array of children, may be null if this node has no children */
protected Vector children;
/** optional user object */
transient protected Object userObject;
/** true if the node is able to have children */
protected boolean allowsChildren;
/**
* Creates a tree node that has no parent and no children, but which
* allows children.
*/
public DefaultMutableTreeNode() {
this(null);
}
/**
* Creates a tree node with no parent, no children, but which allows
* children, and initializes it with the specified user object.
*
* @param userObject an Object provided by the user that constitutes
* the node's data
*/
public DefaultMutableTreeNode(Object userObject) {
this(userObject, true);
}
/**
* Creates a tree node with no parent, no children, initialized with
* the specified user object, and that allows children only if
* specified.
*
* @param userObject an Object provided by the user that constitutes
* the node's data
* @param allowsChildren if true, the node is allowed to have child
* nodes -- otherwise, it is always a leaf node
*/
public DefaultMutableTreeNode(Object userObject, boolean allowsChildren) {
super();
parent = null;
this.allowsChildren = allowsChildren;
this.userObject = userObject;
}
//
// Primitives
//
/**
* Removes <code>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 <code>childIndex.
* <code>newChild must not be null and must not be an ancestor of
* this node.
*
* @param newChild the MutableTreeNode to insert under this node
* @param childIndex the index in this node's child array
* where this node is to be inserted
* @exception ArrayIndexOutOfBoundsException if
* <code>childIndex is out of bounds
* @exception IllegalArgumentException if
* <code>newChild is null or is an
* ancestor of this node
* @exception IllegalStateException if this node does not allow
* children
* @see #isNodeDescendant
*/
public void insert(MutableTreeNode newChild, int childIndex) {
if (!allowsChildren) {
throw new IllegalStateException("node does not allow children");
} else if (newChild == null) {
throw new IllegalArgumentException("new child is null");
} else if (isNodeAncestor(newChild)) {
throw new IllegalArgumentException("new child is an ancestor");
}
MutableTreeNode oldParent = (MutableTreeNode)newChild.getParent();
if (oldParent != null) {
oldParent.remove(newChild);
}
newChild.setParent(this);
if (children == null) {
children = new Vector();
}
children.insertElementAt(newChild, 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 <code>MutableTreeNode.
*
* @param childIndex the index in this node's child array
* of the child to remove
* @exception ArrayIndexOutOfBoundsException if
* <code>childIndex is out of bounds
*/
public void remove(int childIndex) {
MutableTreeNode child = (MutableTreeNode)getChildAt(childIndex);
children.removeElementAt(childIndex);
child.setParent(null);
}
/**
* Sets this node's parent to <code>newParent but does not
* change the parent's child array. This method is called from
* <code>insert() and remove() to
* reassign a child's parent, it should not be messaged from anywhere
* else.
*
* @param newParent this node's new parent
*/
@Transient
public void setParent(MutableTreeNode newParent) {
parent = newParent;
}
/**
* Returns this node's parent or null if this node has no parent.
*
* @return this node's parent TreeNode, or null if this node has no parent
*/
public TreeNode getParent() {
return parent;
}
/**
* Returns the child at the specified index in this node's child array.
*
* @param index an index into this node's child array
* @exception ArrayIndexOutOfBoundsException if <code>index
* is out of bounds
* @return the TreeNode in this node's child array at the specified index
*/
public TreeNode getChildAt(int index) {
if (children == null) {
throw new ArrayIndexOutOfBoundsException("node has no children");
}
return (TreeNode)children.elementAt(index);
}
/**
* Returns the number of children of this node.
*
* @return an int giving the number of children of this node
*/
public int getChildCount() {
if (children == null) {
return 0;
} else {
return children.size();
}
}
/**
* 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
* <code>-1. This method performs a linear search and is O(n)
* where n is the number of children.
*
* @param aChild the TreeNode to search for among this node's children
* @exception IllegalArgumentException if <code>aChild
* is null
* @return an int giving the index of the node in this node's child
* array, or <code>-1 if the specified node is a not
* a child of this node
*/
public int getIndex(TreeNode aChild) {
if (aChild == null) {
throw new IllegalArgumentException("argument is null");
}
if (!isNodeChild(aChild)) {
return -1;
}
return children.indexOf(aChild); // linear search
}
/**
* 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.
*
* @return an Enumeration of this node's children
*/
public Enumeration children() {
if (children == null) {
return EMPTY_ENUMERATION;
} else {
return children.elements();
}
}
/**
* Determines whether or not this node is allowed to have children.
* If <code>allows is false, all of this node's children are
* removed.
* <p>
* Note: By default, a node allows children.
*
* @param allows true if this node is allowed to have children
*/
public void setAllowsChildren(boolean allows) {
if (allows != allowsChildren) {
allowsChildren = allows;
if (!allowsChildren) {
removeAllChildren();
}
}
}
/**
* Returns true if this node is allowed to have children.
*
* @return true if this node allows children, else false
*/
public boolean getAllowsChildren() {
return allowsChildren;
}
/**
* Sets the user object for this node to <code>userObject.
*
* @param userObject the Object that constitutes this node's
* user-specified data
* @see #getUserObject
* @see #toString
*/
public void setUserObject(Object userObject) {
this.userObject = userObject;
}
/**
* Returns this node's user object.
*
* @return the Object stored at this node by the user
* @see #setUserObject
* @see #toString
*/
public Object getUserObject() {
return userObject;
}
//
// Derived methods
//
/**
* 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 removeFromParent() {
MutableTreeNode parent = (MutableTreeNode)getParent();
if (parent != null) {
parent.remove(this);
}
}
/**
* Removes <code>aChild from this node's child array, giving it a
* null parent.
*
* @param aChild a child of this node to remove
* @exception IllegalArgumentException if <code>aChild
* is null or is not a child of this node
*/
public void remove(MutableTreeNode aChild) {
if (aChild == null) {
throw new IllegalArgumentException("argument is null");
}
if (!isNodeChild(aChild)) {
throw new IllegalArgumentException("argument is not a child");
}
remove(getIndex(aChild)); // linear search
}
/**
* Removes all of this node's children, setting their parents to null.
* If this node has no children, this method does nothing.
*/
public void removeAllChildren() {
for (int i = getChildCount()-1; i >= 0; i--) {
remove(i);
}
}
/**
* Removes <code>newChild from its parent and makes it a child of
* this node by adding it to the end of this node's child array.
*
* @see #insert
* @param newChild node to add as a child of this node
* @exception IllegalArgumentException if <code>newChild
* is null
* @exception IllegalStateException if this node does not allow
* children
*/
public void add(MutableTreeNode newChild) {
if(newChild != null && newChild.getParent() == this)
insert(newChild, getChildCount() - 1);
else
insert(newChild, getChildCount());
}
//
// Tree Queries
//
/**
* Returns true if <code>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 <code>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.
*
* @see #isNodeDescendant
* @see #getSharedAncestor
* @param anotherNode node to test as an ancestor of this node
* @return true if this node is a descendant of <code>anotherNode
*/
public boolean isNodeAncestor(TreeNode anotherNode) {
if (anotherNode == null) {
return false;
}
TreeNode ancestor = this;
do {
if (ancestor == anotherNode) {
return true;
}
} while((ancestor = ancestor.getParent()) != null);
return false;
}
/**
* Returns true if <code>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 <code>anotherNode is null, returns
* false. This operation is at worst O(h) where h is the distance from the
* root to <code>anotherNode.
*
* @see #isNodeAncestor
* @see #getSharedAncestor
* @param anotherNode node to test as descendant of this node
* @return true if this node is an ancestor of <code>anotherNode
*/
public boolean isNodeDescendant(DefaultMutableTreeNode anotherNode) {
if (anotherNode == null)
return false;
return anotherNode.isNodeAncestor(this);
}
/**
* Returns the nearest common ancestor to this node and <code>aNode.
* Returns null, if no such ancestor exists -- if this node and
* <code>aNode are in different trees or if aNode is
* null. A node is considered an ancestor of itself.
*
* @see #isNodeAncestor
* @see #isNodeDescendant
* @param aNode node to find common ancestor with
* @return nearest ancestor common to this node and <code>aNode,
* or null if none
*/
public TreeNode getSharedAncestor(DefaultMutableTreeNode aNode) {
if (aNode == this) {
return this;
} else if (aNode == null) {
return null;
}
int level1, level2, diff;
TreeNode node1, node2;
level1 = getLevel();
level2 = aNode.getLevel();
if (level2 > level1) {
diff = level2 - level1;
node1 = aNode;
node2 = this;
} else {
diff = level1 - level2;
node1 = this;
node2 = aNode;
}
// Go up the tree until the nodes are at the same level
while (diff > 0) {
node1 = node1.getParent();
diff--;
}
// Move up the tree until we find a common ancestor. Since we know
// that both nodes are at the same level, we won't cross paths
// unknowingly (if there is a common ancestor, both nodes hit it in
// the same iteration).
do {
if (node1 == node2) {
return node1;
}
node1 = node1.getParent();
node2 = node2.getParent();
} while (node1 != null);// only need to check one -- they're at the
// same level so if one is null, the other is
if (node1 != null || node2 != null) {
throw new Error ("nodes should be null");
}
return null;
}
/**
* Returns true if and only if <code>aNode is in the same tree
* as this node. Returns false if <code>aNode is null.
*
* @see #getSharedAncestor
* @see #getRoot
* @return true if <code>aNode is in the same tree as this node;
* false if <code>aNode is null
*/
public boolean isNodeRelated(DefaultMutableTreeNode aNode) {
return (aNode != null) && (getRoot() == aNode.getRoot());
}
/**
* 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
* <code>getLevel() because it must effectively traverse the entire
* tree rooted at this node.
*
* @see #getLevel
* @return the depth of the tree whose root is this node
*/
public int getDepth() {
Object last = null;
Enumeration enum_ = breadthFirstEnumeration();
while (enum_.hasMoreElements()) {
last = enum_.nextElement();
}
if (last == null) {
throw new Error ("nodes should be null");
}
return ((DefaultMutableTreeNode)last).getLevel() - 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.
*
* @see #getDepth
* @return the number of levels above this node
*/
public int getLevel() {
TreeNode ancestor;
int levels = 0;
ancestor = this;
while((ancestor = ancestor.getParent()) != null){
levels++;
}
return levels;
}
/**
* Returns the path from the root, to get to this node. The last
* element in the path is this node.
*
* @return 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 TreeNode[] getPath() {
return getPathToRoot(this, 0);
}
/**
* 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.
*
* @param aNode the TreeNode to get the path for
* @param depth an int giving the number of steps already taken towards
* the root (on recursive calls), used to size the returned array
* @return an array of TreeNodes giving the path from the root to the
* specified node
*/
protected TreeNode[] getPathToRoot(TreeNode aNode, int depth) {
TreeNode[] retNodes;
/* Check for null, in case someone passed in a null node, or
they passed in an element that isn't rooted at root. */
if(aNode == null) {
if(depth == 0)
return null;
else
retNodes = new TreeNode[depth];
}
else {
depth++;
retNodes = getPathToRoot(aNode.getParent(), depth);
retNodes[retNodes.length - depth] = aNode;
}
return retNodes;
}
/**
* 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 Object[] getUserObjectPath() {
TreeNode[] realPath = getPath();
Object[] retPath = new Object[realPath.length];
for(int counter = 0; counter < realPath.length; counter++)
retPath[counter] = ((DefaultMutableTreeNode)realPath[counter])
.getUserObject();
return retPath;
}
/**
* Returns the root of the tree that contains this node. The root is
* the ancestor with a null parent.
*
* @see #isNodeAncestor
* @return the root of the tree that contains this node
*/
public TreeNode getRoot() {
TreeNode ancestor = this;
TreeNode previous;
do {
previous = ancestor;
ancestor = ancestor.getParent();
} while (ancestor != null);
return previous;
}
/**
* 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.
*
* @return true if this node is the root of its tree
*/
public boolean isRoot() {
return getParent() == null;
}
/**
* 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.
*
* @see #preorderEnumeration
* @return the node that follows this node in a preorder traversal, or
* null if this node is last
*/
public DefaultMutableTreeNode getNextNode() {
if (getChildCount() == 0) {
// No children, so look for nextSibling
DefaultMutableTreeNode nextSibling = getNextSibling();
if (nextSibling == null) {
DefaultMutableTreeNode aNode = (DefaultMutableTreeNode)getParent();
do {
if (aNode == null) {
return null;
}
nextSibling = aNode.getNextSibling();
if (nextSibling != null) {
return nextSibling;
}
aNode = (DefaultMutableTreeNode)aNode.getParent();
} while(true);
} else {
return nextSibling;
}
} else {
return (DefaultMutableTreeNode)getChildAt(0);
}
}
/**
* Returns the node that precedes this node in a preorder traversal of
* this node's tree. Returns <code>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.
*
* @see #preorderEnumeration
* @return the node that precedes this node in a preorder traversal, or
* null if this node is the first
*/
public DefaultMutableTreeNode getPreviousNode() {
DefaultMutableTreeNode previousSibling;
DefaultMutableTreeNode myParent = (DefaultMutableTreeNode)getParent();
if (myParent == null) {
return null;
}
previousSibling = getPreviousSibling();
if (previousSibling != null) {
if (previousSibling.getChildCount() == 0)
return previousSibling;
else
return previousSibling.getLastLeaf();
} else {
return myParent;
}
}
/**
* Creates and returns an enumeration that traverses the subtree rooted at
* this node in preorder. The first node returned by the enumeration's
* <code>nextElement() method is this node.
*
* Modifying the tree by inserting, removing, or moving a node invalidates
* any enumerations created before the modification.
*
* @see #postorderEnumeration
* @return an enumeration for traversing the tree in preorder
*/
public Enumeration preorderEnumeration() {
return new PreorderEnumeration(this);
}
/**
* Creates and returns an enumeration that traverses the subtree rooted at
* this node in postorder. The first node returned by the enumeration's
* <code>nextElement() method is the leftmost leaf. This is the
* same as a depth-first traversal.<P>
*
* Modifying the tree by inserting, removing, or moving a node invalidates
* any enumerations created before the modification.
*
* @see #depthFirstEnumeration
* @see #preorderEnumeration
* @return an enumeration for traversing the tree in postorder
*/
public Enumeration postorderEnumeration() {
return new PostorderEnumeration(this);
}
/**
* 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 <code>nextElement() method is this node.
*
* Modifying the tree by inserting, removing, or moving a node invalidates
* any enumerations created before the modification.
*
* @see #depthFirstEnumeration
* @return an enumeration for traversing the tree in breadth-first order
*/
public Enumeration breadthFirstEnumeration() {
return new BreadthFirstEnumeration(this);
}
/**
* 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 <code>nextElement() method is the leftmost leaf.
* This is the same as a postorder traversal.<P>
*
* Modifying the tree by inserting, removing, or moving a node invalidates
* any enumerations created before the modification.
*
* @see #breadthFirstEnumeration
* @see #postorderEnumeration
* @return an enumeration for traversing the tree in depth-first order
*/
public Enumeration depthFirstEnumeration() {
return postorderEnumeration();
}
/**
* Creates and returns an enumeration that follows the path from
* <code>ancestor to this node. The enumeration's
* <code>nextElement() method first returns ancestor,
* then the child of <code>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 <code>ancestor, inclusive. Each nextElement()
* message is O(1).<P>
*
* Modifying the tree by inserting, removing, or moving a node invalidates
* any enumerations created before the modification.
*
* @see #isNodeAncestor
* @see #isNodeDescendant
* @exception IllegalArgumentException if <code>ancestor is
* not an ancestor of this node
* @return an enumeration for following the path from an ancestor of
* this node to this one
*/
public Enumeration pathFromAncestorEnumeration(TreeNode ancestor) {
return new PathBetweenNodesEnumeration(ancestor, this);
}
//
// Child Queries
//
/**
* Returns true if <code>aNode is a child of this node. If
* <code>aNode is null, this method returns false.
*
* @return true if <code>aNode is a child of this node; false if
* <code>aNode is null
*/
public boolean isNodeChild(TreeNode aNode) {
boolean retval;
if (aNode == null) {
retval = false;
} else {
if (getChildCount() == 0) {
retval = false;
} else {
retval = (aNode.getParent() == this);
}
}
return retval;
}
/**
* Returns this node's first child. If this node has no children,
* throws NoSuchElementException.
*
* @return the first child of this node
* @exception NoSuchElementException if this node has no children
*/
public TreeNode getFirstChild() {
if (getChildCount() == 0) {
throw new NoSuchElementException("node has no children");
}
return getChildAt(0);
}
/**
* Returns this node's last child. If this node has no children,
* throws NoSuchElementException.
*
* @return the last child of this node
* @exception NoSuchElementException if this node has no children
*/
public TreeNode getLastChild() {
if (getChildCount() == 0) {
throw new NoSuchElementException("node has no children");
}
return getChildAt(getChildCount()-1);
}
/**
* Returns the child in this node's child array that immediately
* follows <code>aChild, which must be a child of this node. If
* <code>aChild is the last child, returns null. This method
* performs a linear search of this node's children for
* <code>aChild and is O(n) where n is the number of children; to
* traverse the entire array of children, use an enumeration instead.
*
* @see #children
* @exception IllegalArgumentException if <code>aChild is
* null or is not a child of this node
* @return the child of this node that immediately follows
* <code>aChild
*/
public TreeNode getChildAfter(TreeNode aChild) {
if (aChild == null) {
throw new IllegalArgumentException("argument is null");
}
int index = getIndex(aChild); // linear search
if (index == -1) {
throw new IllegalArgumentException("node is not a child");
}
if (index < getChildCount() - 1) {
return getChildAt(index + 1);
} else {
return null;
}
}
/**
* Returns the child in this node's child array that immediately
* precedes <code>aChild, which must be a child of this node. If
* <code>aChild is the first child, returns null. This method
* performs a linear search of this node's children for <code>aChild
* and is O(n) where n is the number of children.
*
* @exception IllegalArgumentException if <code>aChild is null
* or is not a child of this node
* @return the child of this node that immediately precedes
* <code>aChild
*/
public TreeNode getChildBefore(TreeNode aChild) {
if (aChild == null) {
throw new IllegalArgumentException("argument is null");
}
int index = getIndex(aChild); // linear search
if (index == -1) {
throw new IllegalArgumentException("argument is not a child");
}
if (index > 0) {
return getChildAt(index - 1);
} else {
return null;
}
}
//
// Sibling Queries
//
/**
* Returns true if <code>anotherNode is a sibling of (has the
* same parent as) this node. A node is its own sibling. If
* <code>anotherNode is null, returns false.
*
* @param anotherNode node to test as sibling of this node
* @return true if <code>anotherNode is a sibling of this node
*/
public boolean isNodeSibling(TreeNode anotherNode) {
boolean retval;
if (anotherNode == null) {
retval = false;
} else if (anotherNode == this) {
retval = true;
} else {
TreeNode myParent = getParent();
retval = (myParent != null && myParent == anotherNode.getParent());
if (retval && !((DefaultMutableTreeNode)getParent())
.isNodeChild(anotherNode)) {
throw new Error("sibling has different parent");
}
}
return retval;
}
/**
* 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
* <code>1).
*
* @return the number of siblings of this node
*/
public int getSiblingCount() {
TreeNode myParent = getParent();
if (myParent == null) {
return 1;
} else {
return myParent.getChildCount();
}
}
/**
* 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.
*
* @see #children
* @return the sibling of this node that immediately follows this node
*/
public DefaultMutableTreeNode getNextSibling() {
DefaultMutableTreeNode retval;
DefaultMutableTreeNode myParent = (DefaultMutableTreeNode)getParent();
if (myParent == null) {
retval = null;
} else {
retval = (DefaultMutableTreeNode)myParent.getChildAfter(this); // linear search
}
if (retval != null && !isNodeSibling(retval)) {
throw new Error("child of parent is not a sibling");
}
return retval;
}
/**
* 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.
*
* @return the sibling of this node that immediately precedes this node
*/
public DefaultMutableTreeNode getPreviousSibling() {
DefaultMutableTreeNode retval;
DefaultMutableTreeNode myParent = (DefaultMutableTreeNode)getParent();
if (myParent == null) {
retval = null;
} else {
retval = (DefaultMutableTreeNode)myParent.getChildBefore(this); // linear search
}
if (retval != null && !isNodeSibling(retval)) {
throw new Error("child of parent is not a sibling");
}
return retval;
}
//
// Leaf Queries
//
/**
* Returns true if this node has no children. To distinguish between
* nodes that have no children and nodes that <i>cannot have
* children (e.g. to distinguish files from empty directories), use this
* method in conjunction with <code>getAllowsChildren
*
* @see #getAllowsChildren
* @return true if this node has no children
*/
public boolean isLeaf() {
return (getChildCount() == 0);
}
/**
* 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.
*
* @see #isLeaf
* @see #isNodeDescendant
* @return the first leaf in the subtree rooted at this node
*/
public DefaultMutableTreeNode getFirstLeaf() {
DefaultMutableTreeNode node = this;
while (!node.isLeaf()) {
node = (DefaultMutableTreeNode)node.getFirstChild();
}
return node;
}
/**
* 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.
*
* @see #isLeaf
* @see #isNodeDescendant
* @return the last leaf in the subtree rooted at this node
*/
public DefaultMutableTreeNode getLastLeaf() {
DefaultMutableTreeNode node = this;
while (!node.isLeaf()) {
node = (DefaultMutableTreeNode)node.getLastChild();
}
return node;
}
/**
* Returns the leaf after this node or null if this node is the
* last leaf in the tree.
* <p>
* In this implementation of the <code>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.
* <p>
* 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 <code>depthFirstEnumeration
* to enumerate the nodes in the tree and use <code>isLeaf
* on each node to determine which are leaves.
*
* @see #depthFirstEnumeration
* @see #isLeaf
* @return returns the next leaf past this node
*/
public DefaultMutableTreeNode getNextLeaf() {
DefaultMutableTreeNode nextSibling;
DefaultMutableTreeNode myParent = (DefaultMutableTreeNode)getParent();
if (myParent == null)
return null;
nextSibling = getNextSibling(); // linear search
if (nextSibling != null)
return nextSibling.getFirstLeaf();
return myParent.getNextLeaf(); // tail recursion
}
/**
* Returns the leaf before this node or null if this node is the
* first leaf in the tree.
* <p>
* In this implementation of the <code>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.
* <p>
* 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 <code>depthFirstEnumeration
* to enumerate the nodes in the tree and use <code>isLeaf
* on each node to determine which are leaves.
*
* @see #depthFirstEnumeration
* @see #isLeaf
* @return returns the leaf before this node
*/
public DefaultMutableTreeNode getPreviousLeaf() {
DefaultMutableTreeNode previousSibling;
DefaultMutableTreeNode myParent = (DefaultMutableTreeNode)getParent();
if (myParent == null)
return null;
previousSibling = getPreviousSibling(); // linear search
if (previousSibling != null)
return previousSibling.getLastLeaf();
return myParent.getPreviousLeaf(); // tail recursion
}
/**
* Returns the total number of leaves that are descendants of this node.
* If this node is a leaf, returns <code>1. This method is O(n)
* where n is the number of descendants of this node.
*
* @see #isNodeAncestor
* @return the number of leaves beneath this node
*/
public int getLeafCount() {
int count = 0;
TreeNode node;
Enumeration enum_ = breadthFirstEnumeration(); // order matters not
while (enum_.hasMoreElements()) {
node = (TreeNode)enum_.nextElement();
if (node.isLeaf()) {
count++;
}
}
if (count < 1) {
throw new Error("tree has zero leaves");
}
return count;
}
//
// Overrides
//
/**
* Returns the result of sending <code>toString() to this node's
* user object, or the empty string if the node has no user object.
*
* @see #getUserObject
*/
public String toString() {
if (userObject == null) {
return "";
} else {
return userObject.toString();
}
}
/**
* 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.
*
* @return a copy of this node
*/
public Object clone() {
DefaultMutableTreeNode newNode;
try {
newNode = (DefaultMutableTreeNode)super.clone();
// shallow copy -- the new node has no parent or children
newNode.children = null;
newNode.parent = null;
} catch (CloneNotSupportedException e) {
// Won't happen because we implement Cloneable
throw new Error(e.toString());
}
return newNode;
}
// Serialization support.
private void writeObject(ObjectOutputStream s) throws IOException {
Object[] tValues;
s.defaultWriteObject();
// Save the userObject, if its Serializable.
if(userObject != null && userObject instanceof Serializable) {
tValues = new Object[2];
tValues[0] = "userObject";
tValues[1] = userObject;
}
else
tValues = new Object[0];
s.writeObject(tValues);
}
private void readObject(ObjectInputStream s)
throws IOException, ClassNotFoundException {
Object[] tValues;
s.defaultReadObject();
tValues = (Object[])s.readObject();
if(tValues.length > 0 && tValues[0].equals("userObject"))
userObject = tValues[1];
}
private final class PreorderEnumeration implements Enumeration<TreeNode> {
private final Stack<Enumeration> stack = new Stack();
public PreorderEnumeration(TreeNode rootNode) {
super();
Vector<TreeNode> v = new Vector(1);
v.addElement(rootNode); // PENDING: don't really need a vector
stack.push(v.elements());
}
public boolean hasMoreElements() {
return (!stack.empty() && stack.peek().hasMoreElements());
}
public TreeNode nextElement() {
Enumeration enumer = stack.peek();
TreeNode node = (TreeNode)enumer.nextElement();
Enumeration children = node.children();
if (!enumer.hasMoreElements()) {
stack.pop();
}
if (children.hasMoreElements()) {
stack.push(children);
}
return node;
}
} // End of class PreorderEnumeration
final class PostorderEnumeration implements Enumeration<TreeNode> {
protected TreeNode root;
protected Enumeration<TreeNode> children;
protected Enumeration<TreeNode> subtree;
public PostorderEnumeration(TreeNode rootNode) {
super();
root = rootNode;
children = root.children();
subtree = EMPTY_ENUMERATION;
}
public boolean hasMoreElements() {
return root != null;
}
public TreeNode nextElement() {
TreeNode retval;
if (subtree.hasMoreElements()) {
retval = subtree.nextElement();
} else if (children.hasMoreElements()) {
subtree = new PostorderEnumeration(children.nextElement());
retval = subtree.nextElement();
} else {
retval = root;
root = null;
}
return retval;
}
} // End of class PostorderEnumeration
final class BreadthFirstEnumeration implements Enumeration<TreeNode> {
protected Queue queue;
public BreadthFirstEnumeration(TreeNode rootNode) {
super();
Vector<TreeNode> v = new Vector(1);
v.addElement(rootNode); // PENDING: don't really need a vector
queue = new Queue();
queue.enqueue(v.elements());
}
public boolean hasMoreElements() {
return (!queue.isEmpty() &&
((Enumeration)queue.firstObject()).hasMoreElements());
}
public TreeNode nextElement() {
Enumeration enumer = (Enumeration)queue.firstObject();
TreeNode node = (TreeNode)enumer.nextElement();
Enumeration children = node.children();
if (!enumer.hasMoreElements()) {
queue.dequeue();
}
if (children.hasMoreElements()) {
queue.enqueue(children);
}
return node;
}
// A simple queue with a linked list data structure.
final class Queue {
QNode head; // null if empty
QNode tail;
final class QNode {
public Object object;
public QNode next; // null if end
public QNode(Object object, QNode next) {
this.object = object;
this.next = next;
}
}
public void enqueue(Object anObject) {
if (head == null) {
head = tail = new QNode(anObject, null);
} else {
tail.next = new QNode(anObject, null);
tail = tail.next;
}
}
public Object dequeue() {
if (head == null) {
throw new NoSuchElementException("No more elements");
}
Object retval = head.object;
QNode oldHead = head;
head = head.next;
if (head == null) {
tail = null;
} else {
oldHead.next = null;
}
return retval;
}
public Object firstObject() {
if (head == null) {
throw new NoSuchElementException("No more elements");
}
return head.object;
}
public boolean isEmpty() {
return head == null;
}
} // End of class Queue
} // End of class BreadthFirstEnumeration
final class PathBetweenNodesEnumeration implements Enumeration<TreeNode> {
protected Stack<TreeNode> stack;
public PathBetweenNodesEnumeration(TreeNode ancestor,
TreeNode descendant)
{
super();
if (ancestor == null || descendant == null) {
throw new IllegalArgumentException("argument is null");
}
TreeNode current;
stack = new Stack<TreeNode>();
stack.push(descendant);
current = descendant;
while (current != ancestor) {
current = current.getParent();
if (current == null && descendant != ancestor) {
throw new IllegalArgumentException("node " + ancestor +
" is not an ancestor of " + descendant);
}
stack.push(current);
}
}
public boolean hasMoreElements() {
return stack.size() > 0;
}
public TreeNode nextElement() {
try {
return stack.pop();
} catch (EmptyStackException e) {
throw new NoSuchElementException("No more elements");
}
}
} // End of class PathBetweenNodesEnumeration
} // End of class DefaultMutableTreeNode
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