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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) 2002-2008, 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.directory;

import java.io.File;

/**
 * Performs a last updated check each time isStale is called. Accurate, but will incur in
 * scalability issues under heavy multithreaded load on servers (file access is typically expensive
 * as it requires a switch to kernel space)
 *
 * @author Andrea Aime
 */
class ImmediateDirectoryWatcher implements DirectoryWatcher {

    File directory;

    Long lastUpdated;

    public ImmediateDirectoryWatcher(File directory) {
        this.directory = directory;
    }

    public synchronized boolean isStale() {
        return lastUpdated == null || lastUpdated < directory.lastModified();
    }

    public synchronized void mark() {
        lastUpdated = directory.lastModified();
    }
}