001/*
002 * ModeShape (http://www.modeshape.org)
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *       http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016package org.modeshape.common.collection;
017
018import java.util.Iterator;
019
020/**
021 * An iterator that abstracts iterating over two other iterators.
022 * 
023 * @param <T> the type
024 * @author Randall Hauch (rhauch@redhat.com)
025 */
026public class SequentialIterator<T> implements Iterator<T> {
027
028    public static <T> SequentialIterator<T> create( Iterator<T> first,
029                                                    Iterator<T> second ) {
030        return new SequentialIterator<T>(first, second);
031    }
032
033    private final Iterator<T> first;
034    private final Iterator<T> second;
035    private boolean completedFirst = false;
036
037    public SequentialIterator( Iterator<T> first,
038                               Iterator<T> second ) {
039        this.first = first;
040        this.second = second;
041    }
042
043    @Override
044    public boolean hasNext() {
045        if (!completedFirst) {
046            if (first.hasNext()) return true;
047            completedFirst = true;
048        }
049        return second.hasNext();
050    }
051
052    @Override
053    public T next() {
054        if (!completedFirst) {
055            if (first.hasNext()) return first.next();
056            completedFirst = true;
057        }
058        return second.next();
059    }
060
061    @Override
062    public void remove() {
063        if (!completedFirst) {
064            first.remove();
065        }
066        second.remove();
067    }
068
069}