TermIterator.java

/*
 * 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.dkpro.core.frequency.tfidf.util;

import java.util.Iterator;
import java.util.Map.Entry;

import org.apache.uima.analysis_engine.AnalysisEngineProcessException;
import org.apache.uima.cas.text.AnnotationFS;
import org.apache.uima.jcas.JCas;

import de.tudarmstadt.ukp.dkpro.core.api.featurepath.FeaturePathException;
import de.tudarmstadt.ukp.dkpro.core.api.featurepath.FeaturePathFactory;

/**
 * Iterator over terms (Strings) in the JCas.
 * 
 */
public class TermIterator
    implements Iterable<String>, Iterator<String>
{

    private Iterator<Entry<AnnotationFS, String>> fp;
    private boolean convertToLowercase;

    private TermIterator(Iterable<Entry<AnnotationFS, String>> fp, boolean convertToLowercase)
    {
        super();
        this.fp = fp.iterator();
        this.convertToLowercase = convertToLowercase;
    }

    /**
     * Create a Iterator over all represented strings (specified with the featurePath) in the JCas.
     * 
     * @param jcas
     *            Iterate over all specified Annotations in this jcas
     * @param featurePath
     *            Specifies the annotation and its string representation method.
     * @param convertToLowercase
     *            The terms are converted as specified with this parameter
     * @return an iterator.
     * @throws AnalysisEngineProcessException
     *             if the feature path is invalid.
     */
    public static TermIterator create(JCas jcas, String featurePath, boolean convertToLowercase)
        throws AnalysisEngineProcessException
    {

        try {
            return new TermIterator(FeaturePathFactory.select(jcas.getCas(), featurePath),
                    convertToLowercase);
        }
        catch (FeaturePathException e) {
            throw new AnalysisEngineProcessException(e);
        }
    }

    @Override
    public Iterator<String> iterator()
    {
        return this;
    }

    @Override
    public boolean hasNext()
    {
        return fp.hasNext();
    }

    @Override
    public String next()
    {
        return convertToLowercase ? fp.next().getValue().toLowerCase() : fp.next().getValue();
    }

    @Override
    public void remove()
    {
        fp.remove();
    }

}