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JWKTL (Java Wiktionary Library) is a Java-based API that enables efficient and structured access to the information encoded in the English and the German Wiktionary edition, including sense definitions, part of speech tags, etymology, example sentences, translations, semantic relations and many other lexical information types.

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/*******************************************************************************
 * Copyright 2013
 * Ubiquitous Knowledge Processing (UKP) Lab
 * Technische Universität Darmstadt
 * 
 * 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 de.tudarmstadt.ukp.jwktl.api.util;

import java.util.Iterator;

/**
 * Generic implementation for an iterator of iterators. That is, an object, 
 * which is initialized with an iterator of type OuterType. This iterator is 
 * being iterated an converted into an iterator of type IterableType. For each
 * element of the outer iterator, all elements of the inner iterator are then
 * traversed. For example, a hierarchical iterator of outer type 
 * WiktionaryEntry and inner type WiktionarySense enumerates all senses of 
 * entry1, then all senses of entry2, etc.
 * @param  The type the inner iterator.
 * @param  The type the outer iterator.
 * @author Christian M. Meyer
 */
public abstract class HierarchicalWiktionaryIterator 
		extends WiktionaryIterator {

	protected Iterator outerIterator;
	protected IWiktionaryIterator innerIterator;
	
	/** Initialize the iterator for the given outer type. */
	public HierarchicalWiktionaryIterator(final Iterator outerIterator) {
		this.outerIterator = outerIterator;
	}
	
	protected IterableType fetchNext() {
		if (innerIterator != null && innerIterator.hasNext())
			return innerIterator.next();
		if (!outerIterator.hasNext())
			return null;
		
		OuterType outer = outerIterator.next();
		innerIterator = getInnerIterator(outer);
		if (innerIterator != null && innerIterator.hasNext())
			return innerIterator.next();
		else
			return null;
	}
	
	protected abstract IWiktionaryIterator getInnerIterator(
			final OuterType outer);

	protected void doClose() {
		if (innerIterator != null)
			innerIterator.close();		
	}
	
}