Java tutorial
/* * LensKit, an open source recommender systems toolkit. * Copyright 2010-2014 LensKit Contributors. See CONTRIBUTORS.md. * Work on LensKit has been funded by the National Science Foundation under * grants IIS 05-34939, 08-08692, 08-12148, and 10-17697. * * This program 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; either version 2.1 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., 51 * Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ package org.lenskit.cli; import net.sourceforge.argparse4j.ArgumentParsers; import net.sourceforge.argparse4j.inf.*; import org.apache.commons.lang3.SystemUtils; import org.lenskit.LenskitInfo; import org.lenskit.cli.util.Logging; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.util.ServiceLoader; /** * Main entry point for lenskit-cli. * * @since 3.0 */ public class Main { private static final Logger logger = LoggerFactory.getLogger(Main.class); public static void main(String[] args) { ArgumentParser parser = ArgumentParsers.newArgumentParser("lenskit") .description("Work with LensKit recommenders and data."); Logging.addLoggingGroup(parser); Subparsers subparsers = parser.addSubparsers().metavar("COMMAND").title("commands"); ServiceLoader<Command> loader = ServiceLoader.load(Command.class); for (Command cmd : loader) { Subparser cp = subparsers.addParser(cmd.getName()).help(cmd.getHelp()).setDefault("command", cmd); cmd.configureArguments(cp); } try { Namespace options = parser.parseArgs(args); Logging.configureLogging(options); Runtime rt = Runtime.getRuntime(); logger.info("Starting LensKit {} on Java {} from {}", LenskitInfo.lenskitVersion(), SystemUtils.JAVA_VERSION, SystemUtils.JAVA_VENDOR); logger.debug("Built from Git revision {}", LenskitInfo.getHeadRevision()); logger.debug("Using VM '{}' version {} from {}", SystemUtils.JAVA_VM_NAME, SystemUtils.JAVA_VM_VERSION, SystemUtils.JAVA_VM_VENDOR); logger.info("Have {} processors and heap limit of {} MiB", rt.availableProcessors(), rt.maxMemory() >> 20); Command cmd = options.get("command"); cmd.execute(options); logger.info("If you use LensKit in published research, please see http://lenskit.org/research/"); } catch (ArgumentParserException e) { parser.handleError(e); System.exit(1); } catch (Exception e) { logger.error("error running command: " + e, e); System.exit(2); } } }