javax.swing.text
public class: ElementIterator [javadoc |
source]
java.lang.Object
javax.swing.text.ElementIterator
All Implemented Interfaces:
Cloneable
ElementIterator, as the name suggests, iteratates over the Element
tree. The constructor can be invoked with either Document or an Element
as an argument. If the constructor is invoked with a Document as an
argument then the root of the iteration is the return value of
document.getDefaultRootElement().
The iteration happens in a depth-first manner. In terms of how
boundary conditions are handled:
a) if next() is called before first() or current(), the
root will be returned.
b) next() returns null to indicate the end of the list.
c) previous() returns null when the current element is the root
or next() has returned null.
The ElementIterator does no locking of the Element tree. This means
that it does not track any changes. It is the responsibility of the
user of this class, to ensure that no changes happen during element
iteration.
Simple usage example:
public void iterate() {
ElementIterator it = new ElementIterator(root);
Element elem;
while (true) {
if ((elem = next()) != null) {
// process element
System.out.println("elem: " + elem.getName());
} else {
break;
}
}
}
| Constructor: |
|---|
 public ElementIterator(Document document) {
root = document.getDefaultRootElement();
}
Creates a new ElementIterator. The
root element is taken to get the
default root element of the document. Parameters:
document - a Document.
|
public ElementIterator(Element root) {
this.root = root;
} Creates a new ElementIterator. Parameters:
root - the root Element.
|
| Methods from java.lang.Object: |
|---|
|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Method from javax.swing.text.ElementIterator Detail: |
|---|
public synchronized Object clone() {
try {
ElementIterator it = new ElementIterator(root);
if (elementStack != null) {
it.elementStack = new Stack< StackItem >();
for (int i = 0; i < elementStack.size(); i++) {
StackItem item = elementStack.elementAt(i);
StackItem clonee = (StackItem)item.clone();
it.elementStack.push(clonee);
}
}
return it;
} catch (CloneNotSupportedException e) {
throw new InternalError();
}
} Clones the ElementIterator. |
public Element current() {
if (elementStack == null) {
return first();
}
/*
get a handle to the element on top of the stack.
*/
if (! elementStack.empty()) {
StackItem item = elementStack.peek();
Element elem = item.getElement();
int index = item.getIndex();
// self reference
if (index == -1) {
return elem;
}
// return the child at location "index".
return elem.getElement(index);
}
return null;
} Fetches the current Element. |
public int depth() {
if (elementStack == null) {
return 0;
}
return elementStack.size();
} Fetches the current depth of element tree. |
public Element first() {
// just in case...
if (root == null) {
return null;
}
elementStack = new Stack< StackItem >();
if (root.getElementCount() != 0) {
elementStack.push(new StackItem(root));
}
return root;
} Fetches the first element. |
public Element next() {
/* if current() has not been invoked
and next is invoked, the very first
element will be returned. */
if (elementStack == null) {
return first();
}
// no more elements
if (elementStack.isEmpty()) {
return null;
}
// get a handle to the element on top of the stack
StackItem item = elementStack.peek();
Element elem = item.getElement();
int index = item.getIndex();
if (index+1 < elem.getElementCount()) {
Element child = elem.getElement(index+1);
if (child.isLeaf()) {
/* In this case we merely want to increment
the child index of the item on top of the
stack.*/
item.incrementIndex();
} else {
/* In this case we need to push the child(branch)
on the stack so that we can iterate over its
children. */
elementStack.push(new StackItem(child));
}
return child;
} else {
/* No more children for the item on top of the
stack therefore pop the stack. */
elementStack.pop();
if (!elementStack.isEmpty()) {
/* Increment the child index for the item that
is now on top of the stack. */
StackItem top = elementStack.peek();
top.incrementIndex();
/* We now want to return its next child, therefore
call next() recursively. */
return next();
}
}
return null;
} Fetches the next Element. The strategy
used to locate the next element is
a depth-first search. |
public Element previous() {
int stackSize;
if (elementStack == null || (stackSize = elementStack.size()) == 0) {
return null;
}
// get a handle to the element on top of the stack
//
StackItem item = elementStack.peek();
Element elem = item.getElement();
int index = item.getIndex();
if (index > 0) {
/* return child at previous index. */
return getDeepestLeaf(elem.getElement(--index));
} else if (index == 0) {
/* this implies that current is the element's
first child, therefore previous is the
element itself. */
return elem;
} else if (index == -1) {
if (stackSize == 1) {
// current is the root, nothing before it.
return null;
}
/* We need to return either the item
below the top item or one of the
former's children. */
StackItem top = elementStack.pop();
item = elementStack.peek();
// restore the top item.
elementStack.push(top);
elem = item.getElement();
index = item.getIndex();
return ((index == -1) ? elem : getDeepestLeaf(elem.getElement
(index)));
}
// should never get here.
return null;
} Fetches the previous Element. If howver the current
element is the last element, or the current element
is null, then null is returned. |