conditionexamplereader.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;

/** This ExampleReader skips all examples that do not fulfil a 
 *  specified {@link Condition}.
 *
 *  @version $Id: ConditionExampleReader.java,v 2.5 2003/07/03 16:01:30 fischer Exp $
 */
public class ConditionExampleReader implements ExampleReader {

    /** Array of fully qualified classnames of implementations of
     *  {@link Condition} that are useful independently
     *  of special applications. */
    public static final String[] KNOWN_CONDITION_IMPLEMENTATIONS = {
	AttributeValueFilter.class.getName(),
	LegalNumberCondition.class.getName()
    };

    /** The example reader that provides a complete example set
     *  which must have a cluster attribute set. */
    private ExampleReader parent;

    private Condition condition;

    /** The example that will be returned by the next invocation of next(). */
    private Example currentExample;

    /** Constructs a new ConditionExampleReader the next() method of which
     *  returns only examples that fulfil a specified condition. */
    public ConditionExampleReader(ExampleReader parent, Condition condition) {
	this.parent = parent;
	this.currentExample = null;
	this.condition = condition;
    }

    public boolean hasNext() {
	while (currentExample == null) {
	    if (!parent.hasNext()) return false;
	    Example e = parent.next();
	    if (condition.conditionOk(e))
		currentExample = e;
	}
	return true;
    }

    public Example next() {
	hasNext();
	Example dummy = currentExample;
	currentExample = null;
	return dummy;
    }

    /** Creates a new instance of className which must be an implementation 
     *  of {@link Condition} by calling its two argument constructor passing
     *  it the example set and the  parameter string */
    public static Condition createCondition(String className, 
					    ExampleSet exampleSet, 
					    String parameterString) {

	try {
	    Class clazz = Class.forName(className);
	    if (!Condition.class.isAssignableFrom(clazz))
		throw new ClassCastException("'"+className+"' does not implement Condition!");
	    java.lang.reflect.Constructor constructor = 
		clazz.getConstructor(new Class[] { ExampleSet.class, String.class });
	    return (Condition)constructor.newInstance(new Object[] { exampleSet, parameterString } );
	} catch (ClassNotFoundException e) {
	    throw new RuntimeException("Cannot find class '"+className+"'. Check your classpath.");
	} catch (NoSuchMethodException e) {
	    throw new RuntimeException("'"+className+"' must implement two argument constructor "+
				       className+"(ExampleSet,String) !");
	} catch (java.lang.reflect.InvocationTargetException e) {
	    throw new RuntimeException("Cannot create "+className+": "+e+
				       ". Target: "+e.getCause()+". Cause: "+e.getTargetException()+".");
  	} catch (Throwable throwable) {
  	    throw new RuntimeException("While creating condition '"+className+"': "+throwable);
  	} 
    }
}