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/**
* Copyright 2011 Link Intersystems GmbH
*
* Licensed 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 com.link_intersystems.graph;
import java.util.*;
import static java.util.Objects.requireNonNull;
/**
* Iterator that implements the breadth first traversal strategy for iterating
* {@link Node}s.
*
* @author René Link [rene.link@link-
* intersystems.com]
* @since 1.0.0;
*/
public class BreadthFirstNodeIterator implements Iterator {
private Queue queue = new LinkedList();
/**
* New iterator that starts at the given {@link Node}.
*
* @param startNode the node to start the breadth first traversal from.
* @since 1.0.0;
*/
public BreadthFirstNodeIterator(Node startNode) {
queue.offer(requireNonNull(startNode, "startNode"));
}
/**
* {@inheritDoc}
*
* @since 1.0.0;
*/
public boolean hasNext() {
return !queue.isEmpty();
}
/**
* {@inheritDoc}
*
* @since 1.0.0;
*/
public Node next() {
if (hasNext()) {
Node next = queue.poll();
Collection references = next.getReferences();
queue.addAll(references);
return next;
} else {
throw new NoSuchElementException();
}
}
/**
* Not implemented for {@link Node}s.
*
* @throws UnsupportedOperationException
* @since 1.0.0;
*/
public void remove() {
throw new UnsupportedOperationException("remove operation is not supported.");
}
}