yacy_search_server/source/net/yacy/document/language/Identificator.java

// Identificator.java
// -----------------------
// (C) by Marc Nause; marc.nause@audioattack.de
// first published on http://www.yacy.net
// Braunschweig, Germany, 2008
//
// $LastChangedDate$
// $LastChangedRevision$
// $LastChangedBy$
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

package net.yacy.document.language;

import java.io.File;
import java.util.ArrayList;
import com.cybozu.labs.langdetect.Detector;
import com.cybozu.labs.langdetect.DetectorFactory;
import com.cybozu.labs.langdetect.LangDetectException;
import com.cybozu.labs.langdetect.Language;

import net.yacy.cora.util.ConcurrentLog;

/**
 * This class can try to identify the language a text is written in.
 */
public final class Identificator {

    private Detector detector;
    private Language language;

    public Identificator() {
        try {
            if(DetectorFactory.getLangList().isEmpty()) DetectorFactory.loadProfile(new File("langdetect").toString());
            this.detector = DetectorFactory.create();
        } catch (LangDetectException e) {
            ConcurrentLog.logException(e);
        }
    }

    public void add(final String word) {
        if (word == null) return;
        this.detector.append(" " + word); // detector internally caches text up to maxtextlen = default = 10000 chars
    }

    public String getLanguage() {
        try {
            ArrayList<Language> probabilities = this.detector.getProbabilities();
            if(probabilities.isEmpty()) return null;
            this.language = this.detector.getProbabilities().get(0);
        } catch (LangDetectException e) {
            // this contains mostly the message "no features in text"
            //ConcurrentLog.logException(e);
            return null;
        }
        // Return language only if probability is higher than 30% to account for missing language profiles
        if (this.language.prob > 0.3) {
            return this.language.lang;
        }

        return null;

    }

}