001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.camel.util;
018
019import java.util.Iterator;
020import java.util.NoSuchElementException;
021
022/**
023 * Compound iterator to iterate over multiple iterators sequentially.
024 */
025public class CompoundIterator<T> implements Iterator<T> {
026
027    final Iterator<Iterator<T>> it;
028    Iterator<T> current;
029
030    public CompoundIterator(Iterable<Iterator<T>> it) {
031        this(it.iterator());
032    }
033
034    public CompoundIterator(Iterator<Iterator<T>> it) {
035        this.it = it;
036        this.current = it.hasNext() ? it.next() : null;
037    }
038
039    @Override
040    public boolean hasNext() {
041        while (current != null) {
042            if (current.hasNext()) {
043                return true;
044            } else {
045                current = it.hasNext() ? it.next() : null;
046            }
047
048        }
049        return false;
050    }
051
052    @Override
053    public T next() {
054        if (current != null) {
055            return current.next();
056        }
057        throw new NoSuchElementException();
058    }
059
060    @Override
061    public void remove() {
062        current.remove();
063    }
064}