/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.tinkerpop.gremlin.util.iterator;
import org.apache.tinkerpop.gremlin.process.traversal.util.FastNoSuchElementException;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
/**
* @author Marko A. Rodriguez (http://markorodriguez.com)
*/
public final class MultiIterator<T> implements Iterator<T>, Serializable {
private final List<Iterator<T>> iterators = new ArrayList<>();
private int current = 0;
public void addIterator(final Iterator<T> iterator) {
this.iterators.add(iterator);
}
@Override
public boolean hasNext() {
if (this.current >= this.iterators.size())
return false;
Iterator<T> currentIterator = this.iterators.get(this.current);
while (true) {
if (currentIterator.hasNext()) {
return true;
} else {
this.current++;
if (this.current >= iterators.size())
break;
currentIterator = iterators.get(this.current);
}
}
return false;
}
@Override
public void remove() {
this.iterators.get(this.current).remove();
}
@Override
public T next() {
if (this.iterators.isEmpty()) throw FastNoSuchElementException.instance();
Iterator<T> currentIterator = iterators.get(this.current);
while (true) {
if (currentIterator.hasNext()) {
return currentIterator.next();
} else {
this.current++;
if (this.current >= iterators.size())
break;
currentIterator = iterators.get(current);
}
}
throw FastNoSuchElementException.instance();
}
public void clear() {
this.iterators.clear();
this.current = 0;
}
}