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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) 2003-2008, 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.data;

import java.io.IOException;
import org.opengis.feature.type.AttributeDescriptor;

/**
 * Attribute Reader that joins.
 *
 * @author Ian Schneider
 * @version $Id$
 */
public class JoiningAttributeReader implements AttributeReader {
    private AttributeReader[] readers;
    private int[] index;
    private AttributeDescriptor[] metaData;

    /**
     * Creates a new instance of JoiningAttributeReader
     *
     * @param readers Readers to join
     */
    public JoiningAttributeReader(AttributeReader[] readers) {
        this.readers = readers;

        this.metaData = joinMetaData(readers);
    }

    private AttributeDescriptor[] joinMetaData(AttributeReader[] readers) {
        int total = 0;
        index = new int[readers.length];

        for (int i = 0, ii = readers.length; i < ii; i++) {
            index[i] = total;
            total += readers[i].getAttributeCount();
        }

        AttributeDescriptor[] md = new AttributeDescriptor[total];
        int idx = 0;

        for (int i = 0, ii = readers.length; i < ii; i++) {
            for (int j = 0, jj = readers[i].getAttributeCount(); j < jj; j++) {
                md[idx] = readers[i].getAttributeType(j);
                idx++;
            }
        }

        return md;
    }

    public void close() throws IOException {
        IOException dse = null;

        for (int i = 0, ii = readers.length; i < ii; i++) {
            try {
                readers[i].close();
            } catch (IOException e) {
                dse = e;
            }
        }

        if (dse != null) {
            throw dse;
        }
    }

    public boolean hasNext() throws IOException {
        for (int i = 0, ii = readers.length; i < ii; i++) {
            if (readers[i].hasNext()) {
                return true;
            }
        }

        return false;
    }

    public void next() throws IOException {
        for (int i = 0, ii = readers.length; i < ii; i++) {
            if (readers[i].hasNext()) {
                readers[i].next();
            }
        }
    }

    public Object read(int idx) throws IOException {
        AttributeReader reader = null;

        for (int i = index.length - 1; i >= 0; i--) {
            if (idx >= index[i]) {
                idx -= index[i];
                reader = readers[i];

                break;
            }
        }

        if (reader == null) {
            throw new ArrayIndexOutOfBoundsException(idx);
        }

        return reader.read(idx);
    }

    public int getAttributeCount() {
        return metaData.length;
    }

    public AttributeDescriptor getAttributeType(int i) {
        return metaData[i];
    }
}