001: /*
002: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
003: *
004: * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
005: *
006: * The contents of this file are subject to the terms of either the GNU
007: * General Public License Version 2 only ("GPL") or the Common
008: * Development and Distribution License("CDDL") (collectively, the
009: * "License"). You may not use this file except in compliance with the
010: * License. You can obtain a copy of the License at
011: * http://www.netbeans.org/cddl-gplv2.html
012: * or nbbuild/licenses/CDDL-GPL-2-CP. See the License for the
013: * specific language governing permissions and limitations under the
014: * License. When distributing the software, include this License Header
015: * Notice in each file and include the License file at
016: * nbbuild/licenses/CDDL-GPL-2-CP. Sun designates this
017: * particular file as subject to the "Classpath" exception as provided
018: * by Sun in the GPL Version 2 section of the License file that
019: * accompanied this code. If applicable, add the following below the
020: * License Header, with the fields enclosed by brackets [] replaced by
021: * your own identifying information:
022: * "Portions Copyrighted [year] [name of copyright owner]"
023: *
024: * Contributor(s):
025: *
026: * The Original Software is NetBeans. The Initial Developer of the Original
027: * Software is Sun Microsystems, Inc. Portions Copyright 1997-2006 Sun
028: * Microsystems, Inc. All Rights Reserved.
029: *
030: * If you wish your version of this file to be governed by only the CDDL
031: * or only the GPL Version 2, indicate your decision by adding
032: * "[Contributor] elects to include this software in this distribution
033: * under the [CDDL or GPL Version 2] license." If you do not indicate a
034: * single choice of license, a recipient has the option to distribute
035: * your version of this file under either the CDDL, the GPL Version 2 or
036: * to extend the choice of license to its licensees as provided above.
037: * However, if you add GPL Version 2 code and therefore, elected the GPL
038: * Version 2 license, then the option applies only if the new code is
039: * made subject to such option by the copyright holder.
040: */
041: package org.netbeans.modules.xml.catalog.lib;
042:
043: import java.util.*;
044:
045: /**
046: * Let a list of iterators behave as a single iterator.
047: *
048: * @author Petr Kuzel
049: */
050: public final class IteratorIterator implements Iterator {
051:
052: private Vector iterators = new Vector();
053:
054: private Iterator current = null; //current iterator;
055: private Iterator it = null; //iterators.iterator();
056:
057: /*
058: * It is set by hasNext() and cleared by next() call.
059: */
060: private Object next = null; //current element
061:
062: /**
063: * New iterators can be added while hasNext() or prior its first call.
064: * @param it iterator, never <codE>null</null>.
065: */
066: public void add(Iterator it) {
067: assert it != null;
068: iterators.add(it);
069: }
070:
071: /**
072: * Unsupported operation.
073: */
074: public void remove() {
075: throw new UnsupportedOperationException();
076: }
077:
078: public Object next() {
079: if (hasNext()) {
080: Object tmp = next;
081: next = null;
082: return tmp;
083: } else {
084: throw new NoSuchElementException();
085: }
086: }
087:
088: public boolean hasNext() {
089: if (next != null)
090: return true;
091:
092: if (it == null)
093: it = iterators.iterator();
094: while (current == null) {
095: if (it.hasNext()) {
096: current = (Iterator) it.next();
097: } else {
098: return false;
099: }
100: }
101:
102: while (current.hasNext() || it.hasNext()) {
103:
104: // fetch next iterator if necessary
105: if (current.hasNext() == false) {
106: current = (Iterator) it.next();
107: continue;
108: } else {
109: next = current.next();
110: return true;
111: }
112: }
113: next = null;
114: return false;
115: }
116: }
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