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The main module contains the GeoTools public interfaces that are used by other GeoTools modules (and GeoTools applications). Where possible we make use industry standard terms as provided by OGC and ISO standards. The formal GeoTools public api consists of gt-metadata, jts and the gt-main module. The main module contains the default implementations that are available provided to other GeoTools modules using our factory system. Factories are obtained from an appropriate FactoryFinder, giving applications a chance configure the factory used using the Factory Hints facilities. FilterFactory ff = CommonFactoryFinder.getFilterFactory(); Expression expr = ff.add( expression1, expression2 ); If you find yourself using implementation specific classes chances are you doing it wrong: Expression expr = new AddImpl( expression1, expressiom2 );

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/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 *
 *    (C) 2005-2008, Open Source Geospatial Foundation (OSGeo)
 *
 *    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;
 *    version 2.1 of the License.
 *
 *    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.
 */
package org.geotools.feature.visitor;

import org.geotools.data.simple.SimpleFeatureCollection;
import org.geotools.feature.visitor.SumVisitor.SumResult;
import org.opengis.feature.simple.SimpleFeature;

/**
 * Determines the number of features in the collection
 *
 * @author Cory Horner, Refractions
 * @since 2.2.M2
 */
public class CountVisitor implements FeatureCalc {
    Integer count = null;

    public void init(SimpleFeatureCollection collection) {
        // do nothing
    }

    public void visit(SimpleFeature feature) {
        visit((org.opengis.feature.Feature) feature);
    }

    public void visit(org.opengis.feature.Feature feature) {
        if (count == null) {
            count = 0;
        }
        count++;
    }

    public int getCount() {
        if (count == null) {
            return 0;
        }
        return count;
    }

    public void setValue(int count) {
        this.count = count;
    }

    public void reset() {
        this.count = null;
    }

    public CalcResult getResult() {
        if (count == null) {
            return CalcResult.NULL_RESULT;
        }
        return new CountResult(count);
    }

    public static class CountResult extends AbstractCalcResult {
        private int count;

        public CountResult(int newcount) {
            count = newcount;
        }

        public Object getValue() {
            return Integer.valueOf(count);
        }

        public boolean isCompatible(CalcResult targetResults) {
            if (targetResults == CalcResult.NULL_RESULT) return true;
            if (targetResults instanceof CountResult) return true;
            if (targetResults instanceof SumResult) return true;
            return false;
        }

        public CalcResult merge(CalcResult resultsToAdd) {
            if (!isCompatible(resultsToAdd)) {
                throw new IllegalArgumentException("Parameter is not a compatible type");
            }

            if (resultsToAdd == CalcResult.NULL_RESULT) {
                return this;
            }

            if (resultsToAdd instanceof CountResult) {
                // add the two counts
                int toAdd = resultsToAdd.toInt();
                return new CountResult(count + toAdd);
            } else if (resultsToAdd instanceof SumResult) {
                // we don't want to implement this twice, so we'll call the
                // SumResult version of this function
                return resultsToAdd.merge(this);
            } else {
                throw new IllegalArgumentException(
                        "The CalcResults claim to be compatible, but the appropriate merge method has not been implemented.");
            }
        }
    }
}