basiccontextgenerator.java

最大熵模型源代码

///////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2001 Jason Baldridge
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library 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 Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser 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 opennlp.maxent;

import java.util.*;

/**
 * Generate contexts for maxent decisions, assuming that the input
 * given to the getContext() method is a String containing contextual
 * predicates separated by spaces, e.g:
 * 
 * <p>
 * cp_1 cp_2 ... cp_n
 * </p>
 * 
 * @author      Jason Baldridge
 * @version     $Revision: 1.2 $, $Date: 2002/04/30 08:48:35 $
 */
public class BasicContextGenerator implements ContextGenerator {

    /**
     * Builds up the list of contextual predicates given a String.
     */
    public String[] getContext(Object o) {
	String s = (String)o;
	int prevIndex = -1;
	int index = s.indexOf(' ');
	List cuts = new ArrayList();
	while (index != -1) {
	    cuts.add(s.substring(prevIndex+1, index));
	    prevIndex = index;
	    index = s.indexOf(' ', ++index);
	}
	cuts.add(s.substring(prevIndex+1, s.length()));
	return (String[])cuts.toArray(new String[cuts.size()]);
    }
 
}