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

109 lines
3.4 KiB

// 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.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;
/**
* Default constructor. Requires the DetectorFactory language profiles to be loaded before.
*/
public Identificator() {
try {
this.detector = DetectorFactory.create();
} catch (LangDetectException e) {
ConcurrentLog.logException(e);
}
}
/**
* Append a word to the text to be analyzed.
* Analysis takes letter case into account (this means word should not be upper- or lower cased)
* @param word
*/
public void add(final String word) {
if (word == null || this.detector == null) {
return;
}
this.detector.append(" " + word); // detector internally caches text up to maxtextlen = default = 10000 chars
}
/**
* Get the detected language with highest probability
* if detection probability is above 0.3 (30%)
* Underlying detector differentiates zh-cn and zh-tw, these are returned as zh here.
* @return 2 char language code (ISO 639-1)
*/
public String getLanguage() {
if(this.detector != null) {
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) {
if (this.language.lang.length() == 2) {
return this.language.lang;
}
return this.language.lang.substring(0,2);
}
}
return null;
}
/**
* Get the probability of the detected language (returned by {@link #getLanguage()})
* @return 0.0 to 1.0
*/
public double getProbability() {
if (language != null) {
return language.prob;
}
return 0.0;
}
}