edu.byu.nlp.data.streams.StopWordRemover.java Source code

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Here is the source code for edu.byu.nlp.data.streams.StopWordRemover.java

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/**
 * Copyright 2012 Brigham Young University
 *
 * 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 edu.byu.nlp.data.streams;

import java.util.Set;

import com.google.common.base.Function;
import com.google.common.collect.Sets;

import edu.byu.nlp.io.Files2;

/**
 * @author rah67
 *
 */
public class StopWordRemover implements Function<String, String> {

    private static final String MALLET_STOP_WORDS_FILE = "/mallet_stopwords.txt";
    private static final String TWITTER_STOP_WORDS_FILE = "/twitter_stopwords.txt";

    private Set<String> stopWords;

    public StopWordRemover(Set<String> stopWords) {
        this.stopWords = stopWords;
    }

    /** {@inheritDoc} */
    @Override
    public String apply(String word) {
        if (word == null) {
            return null;
        }

        return (stopWords.contains(word.toLowerCase())) ? null : word;
    }

    public static Set<String> malletStopWords() {
        return Sets.newHashSet(Files2.open(StopWordRemover.class, MALLET_STOP_WORDS_FILE));
    }

    public static Set<String> twitterStopWords() {
        return Sets.newHashSet(Files2.open(StopWordRemover.class, TWITTER_STOP_WORDS_FILE));
    }

    public static StopWordRemover fromWords(Set<String> words) {
        return new StopWordRemover(words);
    }

    public static StopWordRemover malletStopWordRemover() {
        return fromWords(malletStopWords());
    }

    public static StopWordRemover twitterStopWordRemover() {
        return fromWords(twitterStopWords());
    }

}