001/* Copyright (C) 2013 TU Dortmund
002 * This file is part of AutomataLib, http://www.automatalib.net/.
003 * 
004 * AutomataLib is free software; you can redistribute it and/or
005 * modify it under the terms of the GNU Lesser General Public
006 * License version 3.0 as published by the Free Software Foundation.
007 * 
008 * AutomataLib is distributed in the hope that it will be useful,
009 * but WITHOUT ANY WARRANTY; without even the implied warranty of
010 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
011 * Lesser General Public License for more details.
012 * 
013 * You should have received a copy of the GNU Lesser General Public
014 * License along with AutomataLib; if not, see
015 * http://www.gnu.de/documents/lgpl.en.html.
016 */
017package net.automatalib.commons.util.collections;
018
019import java.util.Iterator;
020import java.util.NoSuchElementException;
021
022public abstract class TwoLevelIterator<L1, L2, O> implements Iterator<O> {
023        
024        private final Iterator<? extends L1> l1Iterator;
025        private L1 l1Object;
026        private Iterator<L2> l2Iterator;
027        
028        public TwoLevelIterator(Iterator<? extends L1> l1Iterator) {
029                this.l1Iterator = l1Iterator;
030                this.l2Iterator = null;
031        }
032        
033        protected abstract Iterator<L2> l2Iterator(L1 l1Object);
034        
035        protected abstract O combine(L1 l1Object, L2 l2Object);
036        
037        protected void nextL1() {
038                this.l2Iterator = null;
039        }
040        
041        protected boolean advance() {
042                while(l2Iterator == null || !l2Iterator.hasNext()) {
043                        if(!l1Iterator.hasNext())
044                                return false;
045                        this.l1Object = l1Iterator.next();
046                        this.l2Iterator = l2Iterator(this.l1Object);
047                }
048                return true;
049        }
050
051        /* (non-Javadoc)
052         * @see java.util.Iterator#hasNext()
053         */
054        @Override
055        public boolean hasNext() {
056                if(l2Iterator != null && l2Iterator.hasNext())
057                        return true;
058                return advance();
059        }
060
061        /* (non-Javadoc)
062         * @see java.util.Iterator#next()
063         */
064        @Override
065        public O next() {
066                if(l2Iterator == null || !l2Iterator.hasNext()) {
067                        if(!advance())
068                                throw new NoSuchElementException();
069                }
070                return combine(l1Object, l2Iterator.next());    
071        }
072
073        /* (non-Javadoc)
074         * @see java.util.Iterator#remove()
075         */
076        @Override
077        public void remove() {
078                l2Iterator.remove();
079        }
080        
081        
082        
083}