author | malenkov |
Wed, 30 Apr 2014 19:28:05 +0400 | |
changeset 24544 | c0133e7c7162 |
parent 23010 | 6dadb192ad81 |
child 25193 | 187a455af8f8 |
permissions | -rw-r--r-- |
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/* |
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* Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. Oracle designates this |
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* particular file as subject to the "Classpath" exception as provided |
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* by Oracle in the LICENSE file that accompanied this code. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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*/ |
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package javax.swing.text; |
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import java.util.Stack; |
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import java.util.Enumeration; |
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/** |
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* <p> |
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* ElementIterator, as the name suggests, iterates over the Element |
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* tree. The constructor can be invoked with either Document or an Element |
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* as an argument. If the constructor is invoked with a Document as an |
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* argument then the root of the iteration is the return value of |
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* document.getDefaultRootElement(). |
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* |
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* The iteration happens in a depth-first manner. In terms of how |
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* boundary conditions are handled: |
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* a) if next() is called before first() or current(), the |
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* root will be returned. |
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* b) next() returns null to indicate the end of the list. |
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* c) previous() returns null when the current element is the root |
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* or next() has returned null. |
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* |
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* The ElementIterator does no locking of the Element tree. This means |
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* that it does not track any changes. It is the responsibility of the |
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* user of this class, to ensure that no changes happen during element |
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* iteration. |
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* |
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* Simple usage example: |
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* |
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* public void iterate() { |
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* ElementIterator it = new ElementIterator(root); |
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* Element elem; |
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* while (true) { |
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* if ((elem = next()) != null) { |
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* // process element |
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* System.out.println("elem: " + elem.getName()); |
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* } else { |
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* break; |
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* } |
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* } |
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* } |
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* |
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* @author Sunita Mani |
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* |
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*/ |
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public class ElementIterator implements Cloneable { |
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private Element root; |
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private Stack<StackItem> elementStack = null; |
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/** |
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* The StackItem class stores the element |
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* as well as a child index. If the |
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* index is -1, then the element represented |
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* on the stack is the element itself. |
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* Otherwise, the index functions as as index |
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* into the vector of children of the element. |
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* In this case, the item on the stack |
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* represents the "index"th child of the element |
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* |
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*/ |
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private class StackItem implements Cloneable { |
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Element item; |
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int childIndex; |
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private StackItem(Element elem) { |
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/** |
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* -1 index implies a self reference, |
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* as opposed to an index into its |
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* list of children. |
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*/ |
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this.item = elem; |
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this.childIndex = -1; |
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} |
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private void incrementIndex() { |
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childIndex++; |
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} |
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private Element getElement() { |
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return item; |
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} |
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private int getIndex() { |
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return childIndex; |
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} |
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protected Object clone() throws java.lang.CloneNotSupportedException { |
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return super.clone(); |
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} |
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} |
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/** |
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* Creates a new ElementIterator. The |
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* root element is taken to get the |
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* default root element of the document. |
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* |
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* @param document a Document. |
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*/ |
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public ElementIterator(Document document) { |
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root = document.getDefaultRootElement(); |
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} |
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/** |
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* Creates a new ElementIterator. |
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* |
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* @param root the root Element. |
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*/ |
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public ElementIterator(Element root) { |
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this.root = root; |
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} |
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/** |
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* Clones the ElementIterator. |
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* |
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* @return a cloned ElementIterator Object. |
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*/ |
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public synchronized Object clone() { |
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try { |
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ElementIterator it = new ElementIterator(root); |
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if (elementStack != null) { |
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it.elementStack = new Stack<StackItem>(); |
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for (int i = 0; i < elementStack.size(); i++) { |
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StackItem item = elementStack.elementAt(i); |
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StackItem clonee = (StackItem)item.clone(); |
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it.elementStack.push(clonee); |
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} |
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} |
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return it; |
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} catch (CloneNotSupportedException e) { |
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throw new InternalError(e); |
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} |
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} |
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/** |
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* Fetches the first element. |
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* |
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* @return an Element. |
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*/ |
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public Element first() { |
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// just in case... |
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if (root == null) { |
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return null; |
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} |
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elementStack = new Stack<StackItem>(); |
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if (root.getElementCount() != 0) { |
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elementStack.push(new StackItem(root)); |
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} |
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return root; |
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} |
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/** |
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* Fetches the current depth of element tree. |
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* |
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* @return the depth. |
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*/ |
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public int depth() { |
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if (elementStack == null) { |
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return 0; |
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} |
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return elementStack.size(); |
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} |
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/** |
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* Fetches the current Element. |
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* |
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* @return element on top of the stack or |
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* <code>null</code> if the root element is <code>null</code> |
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*/ |
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public Element current() { |
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if (elementStack == null) { |
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return first(); |
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} |
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/* |
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get a handle to the element on top of the stack. |
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*/ |
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if (! elementStack.empty()) { |
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StackItem item = elementStack.peek(); |
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Element elem = item.getElement(); |
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int index = item.getIndex(); |
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// self reference |
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if (index == -1) { |
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return elem; |
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} |
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// return the child at location "index". |
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return elem.getElement(index); |
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} |
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return null; |
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} |
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/** |
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* Fetches the next Element. The strategy |
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* used to locate the next element is |
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* a depth-first search. |
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* |
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* @return the next element or <code>null</code> |
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* at the end of the list. |
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*/ |
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public Element next() { |
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/* if current() has not been invoked |
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and next is invoked, the very first |
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element will be returned. */ |
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if (elementStack == null) { |
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return first(); |
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} |
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// no more elements |
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if (elementStack.isEmpty()) { |
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return null; |
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} |
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// get a handle to the element on top of the stack |
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StackItem item = elementStack.peek(); |
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Element elem = item.getElement(); |
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int index = item.getIndex(); |
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if (index+1 < elem.getElementCount()) { |
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Element child = elem.getElement(index+1); |
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if (child.isLeaf()) { |
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/* In this case we merely want to increment |
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the child index of the item on top of the |
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stack.*/ |
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item.incrementIndex(); |
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} else { |
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/* In this case we need to push the child(branch) |
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on the stack so that we can iterate over its |
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children. */ |
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elementStack.push(new StackItem(child)); |
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} |
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return child; |
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} else { |
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/* No more children for the item on top of the |
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stack therefore pop the stack. */ |
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elementStack.pop(); |
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if (!elementStack.isEmpty()) { |
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/* Increment the child index for the item that |
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is now on top of the stack. */ |
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StackItem top = elementStack.peek(); |
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top.incrementIndex(); |
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/* We now want to return its next child, therefore |
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call next() recursively. */ |
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return next(); |
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} |
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} |
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return null; |
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} |
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/** |
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* Fetches the previous Element. If however the current |
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* element is the last element, or the current element |
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* is null, then null is returned. |
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* |
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* @return previous <code>Element</code> if available |
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* |
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*/ |
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public Element previous() { |
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int stackSize; |
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if (elementStack == null || (stackSize = elementStack.size()) == 0) { |
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return null; |
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} |
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// get a handle to the element on top of the stack |
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// |
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StackItem item = elementStack.peek(); |
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Element elem = item.getElement(); |
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int index = item.getIndex(); |
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if (index > 0) { |
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/* return child at previous index. */ |
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return getDeepestLeaf(elem.getElement(--index)); |
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} else if (index == 0) { |
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/* this implies that current is the element's |
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first child, therefore previous is the |
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element itself. */ |
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return elem; |
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} else if (index == -1) { |
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if (stackSize == 1) { |
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// current is the root, nothing before it. |
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return null; |
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} |
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/* We need to return either the item |
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below the top item or one of the |
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former's children. */ |
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StackItem top = elementStack.pop(); |
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item = elementStack.peek(); |
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// restore the top item. |
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elementStack.push(top); |
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elem = item.getElement(); |
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index = item.getIndex(); |
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return ((index == -1) ? elem : getDeepestLeaf(elem.getElement |
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(index))); |
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} |
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// should never get here. |
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return null; |
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} |
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/** |
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* Returns the last child of <code>parent</code> that is a leaf. If the |
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* last child is a not a leaf, this method is called with the last child. |
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*/ |
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private Element getDeepestLeaf(Element parent) { |
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if (parent.isLeaf()) { |
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return parent; |
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} |
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int childCount = parent.getElementCount(); |
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if (childCount == 0) { |
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return parent; |
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} |
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return getDeepestLeaf(parent.getElement(childCount - 1)); |
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} |
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/* |
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Iterates through the element tree and prints |
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out each element and its attributes. |
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*/ |
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private void dumpTree() { |
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Element elem; |
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while (true) { |
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if ((elem = next()) != null) { |
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System.out.println("elem: " + elem.getName()); |
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AttributeSet attr = elem.getAttributes(); |
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String s = ""; |
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Enumeration names = attr.getAttributeNames(); |
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while (names.hasMoreElements()) { |
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Object key = names.nextElement(); |
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Object value = attr.getAttribute(key); |
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if (value instanceof AttributeSet) { |
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// don't go recursive |
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s = s + key + "=**AttributeSet** "; |
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} else { |
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s = s + key + "=" + value + " "; |
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} |
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} |
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System.out.println("attributes: " + s); |
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} else { |
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break; |
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} |
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} |
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} |
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} |