/*--- formatted by Jindent 2.1, (www.c-lab.de/~jindent) ---*//** * SelectDifference Class * * location: net.openai.ai.ga.selection.common.SelectDifference * */package net.openai.ai.ga.selection.common;import net.openai.ai.ga.selection.*;import net.openai.ai.ga.population.*;import net.openai.ai.ga.cell.*;import java.util.Collection;/** * <code>SelectDifference</code> is a <code>SelectionAlgorithm</code> * that will return the difference of the results of two specified <code> * SelectionAlgorithm</code>s. * * @author	Jared Grubb * @version	%I%, %G% * @since	JDK1.3 */public class SelectDifference implements SelectionAlgorithm {    private SelectionAlgorithm arg1, arg2;    /**     * Creates a new <code>SelectDifference</code> object for taking the     * difference of the <code>Population</code>s returned by the two     * passed <code>SelectionAlgorithm</code>s.     *     * @param first the first <code>SelectionAlgorithm</code>     * @param second the second <code>SelectionAlgorithm</code>     */    public SelectDifference(SelectionAlgorithm first,                       SelectionAlgorithm second) {        this.arg1 = first;        this.arg2 = second;    }    /**     * Returns a <code>Population</code> that represents the difference     * (disjunction) of the two <code>SelectionAlgorithm</code>s specified in     * the constructor. The return is the result of the first selection     * algorithm with the results of the second removed from it via     * <code>Population.removeCells</code> method.     *     * If the first selection algorithm returns a <code>null</code> then a     * <code>NullPointerException</code> will be thrown. If the second one     * returns a <code>null</code>, the the results of the first will be     * returned unchanged.     *     * @param pop  the <code>Population</code> to choose from     * @return the difference <code>Population</code> of the two selection     *         algorithms     */    public Population selectFromPopulation(Population pop) {        Population toReturn = arg1.selectFromPopulation(pop);        toReturn.removeCells(arg2.selectFromPopulation(pop));        return toReturn;    }}/*--- formatting done in "Sun Java Convention" style on 12-28-2000 ---*/