| /******************************************************************************* |
| * Copyright (c) 2005, 2013 Oracle and/or its affiliates. All rights reserved. |
| * This program and the accompanying materials are made available under the |
| * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0 |
| * which accompanies this distribution. |
| * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html |
| * and the Eclipse Distribution License is available at |
| * http://www.eclipse.org/org/documents/edl-v10.php. |
| * |
| * Contributors: |
| * Oracle - initial API and implementation |
| * |
| ******************************************************************************/ |
| package org.eclipse.persistence.tools.utility.iterator; |
| |
| import java.util.Iterator; |
| import java.util.LinkedList; |
| import org.eclipse.persistence.tools.utility.ObjectTools; |
| import org.eclipse.persistence.tools.utility.transformer.Transformer; |
| |
| /** |
| * A <code>TreeIterator</code> simplifies the traversal of a |
| * tree of objects, where the objects' protocol(s) provides |
| * a method for getting the immediate children of the given |
| * node but does not provide a method for getting all the |
| * descendants (children, grandchildren, etc.) of the given node. |
| * <p> |
| * To use, supply:<ul> |
| * <li> either the root element of the tree or, if the tree has |
| * multiple roots, an {@link Iterator} over the set of roots |
| * <li> a {@link Transformer} that delivers the children |
| * of each child |
| * </ul> |
| * |
| * @param <E> the type of elements returned by the iterator |
| * |
| * @see org.eclipse.jpt.common.utility.internal.iterable.TreeIterable |
| */ |
| public class TreeIterator<E> |
| implements Iterator<E> |
| { |
| private final LinkedList<Iterator<? extends E>> iterators; |
| private final Transformer<E, Iterator<? extends E>> transformer; |
| private Iterator<? extends E> currentIterator; |
| |
| |
| /** |
| * Construct an iterator that returns the nodes of a tree |
| * with the specified roots and transformer. |
| */ |
| public TreeIterator(Iterator<? extends E> roots, Transformer<E, Iterator<? extends E>> transformer) { |
| super(); |
| if ((roots == null) || (transformer == null)) { |
| throw new NullPointerException(); |
| } |
| this.currentIterator = roots; |
| // use a LinkedList since we will be pulling off the front and adding to the end |
| this.iterators = new LinkedList<Iterator<? extends E>>(); |
| this.transformer = transformer; |
| } |
| |
| @Override |
| public boolean hasNext() { |
| if (this.currentIterator.hasNext()) { |
| return true; |
| } |
| for (Iterator<? extends E> iterator : this.iterators) { |
| if (iterator.hasNext()) { |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| @Override |
| public E next() { |
| if (this.currentIterator.hasNext()) { |
| return this.nextInternal(); |
| } |
| for (Iterator<Iterator<? extends E>> stream = this.iterators.iterator(); stream.hasNext(); ) { |
| this.currentIterator = stream.next(); |
| if (this.currentIterator.hasNext()) { |
| break; |
| } |
| stream.remove(); |
| } |
| return this.nextInternal(); |
| } |
| |
| /** |
| * Fetch the children of the next node before returning it. |
| */ |
| private E nextInternal() { |
| E next = this.currentIterator.next(); |
| this.iterators.add(this.transformer.transform(next)); |
| return next; |
| } |
| |
| @Override |
| public void remove() { |
| this.currentIterator.remove(); |
| } |
| |
| @Override |
| public String toString() { |
| return ObjectTools.toString(this, this.currentIterator); |
| } |
| } |