splittedexamplesetreader.java

著名的开源仿真软件yale

/*
 *  YALE - Yet Another Learning Environment
 *  Copyright (C) 2002, 2003
 *      Simon Fischer, Ralf Klinkenberg, Ingo Mierswa, 
 *          Katharina Morik, Oliver Ritthoff
 *      Artificial Intelligence Unit
 *      Computer Science Department
 *      University of Dortmund
 *      44221 Dortmund,  Germany
 *  email: [e-mail]
 *  web:   http://yale.cs.uni-dortmund.de/
 *
 *  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 edu.udo.cs.yale.example;

/** Returns only a subset of an example set specified by an instance 
 *  of {@link Partition}.
 *
 *  @version $Id: SplittedExampleSetReader.java,v 2.3 2003/05/01 16:28:27 fischer Exp $
 */
public class SplittedExampleSetReader implements ExampleReader {

    /** The underlying reader. */
    private ExampleReader reader;

    /** Index of the current example. */
    private int current;

    /** The partition. */
    private Partition partition;

    /** The next example that will be returned. */
    private Example next;

    public SplittedExampleSetReader(ExampleReader reader, Partition partition) {
	this.reader    = reader;
	this.partition = partition;
	current        = -1;
	hasNext();
    }

    public boolean hasNext() {
	while (next == null) {
	    current++;

	    Example example = reader.next();
	    if (example == null) return false;

	    if (current >= partition.getTotalSize()) return false;

	    if (partition.isSelected(current))
		next = example;
	}
	return true;
    }

    public Example next() {
	if (!hasNext()) {
	    return null;
	} else {
	    Example dummy = next;
	    next = null;
	    return dummy;
	}
    }

}