Java tutorial
/* * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 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, see <http://www.gnu.org/licenses/>. */ /* * SerializedInstancesLoader.java * Copyright (C) 2002-2012 University of Waikato, Hamilton, New Zealand * */ package weka.core.converters; import java.io.BufferedInputStream; import java.io.IOException; import java.io.InputStream; import java.io.ObjectInputStream; import weka.core.Instance; import weka.core.Instances; import weka.core.RevisionUtils; /** <!-- globalinfo-start --> * Reads a source that contains serialized Instances. * <p/> <!-- globalinfo-end --> * * @author <a href="mailto:len@reeltwo.com">Len Trigg</a> * @version $Revision$ * @see Loader */ public class SerializedInstancesLoader extends AbstractFileLoader implements BatchConverter, IncrementalConverter { /** for serialization */ static final long serialVersionUID = 2391085836269030715L; /** the file extension */ public static String FILE_EXTENSION = Instances.SERIALIZED_OBJ_FILE_EXTENSION; /** Holds the structure (header) of the data set. */ protected Instances m_Dataset = null; /** The current index position for incremental reading */ protected int m_IncrementalIndex = 0; /** * Returns a string describing this object * * @return a description of the classifier suitable for * displaying in the explorer/experimenter gui */ public String globalInfo() { return "Reads a source that contains serialized Instances."; } /** Resets the Loader ready to read a new data set */ public void reset() { m_Dataset = null; m_IncrementalIndex = 0; } /** * Get the file extension used for arff files * * @return the file extension */ public String getFileExtension() { return FILE_EXTENSION; } /** * Gets all the file extensions used for this type of file * * @return the file extensions */ public String[] getFileExtensions() { return new String[] { getFileExtension() }; } /** * Returns a description of the file type. * * @return a short file description */ public String getFileDescription() { return "Binary serialized instances"; } /** * Resets the Loader object and sets the source of the data set to be * the supplied InputStream. * * @param in the source InputStream. * @throws IOException if there is a problem with IO */ public void setSource(InputStream in) throws IOException { ObjectInputStream oi = new ObjectInputStream(new BufferedInputStream(in)); try { m_Dataset = (Instances) oi.readObject(); } catch (ClassNotFoundException ex) { throw new IOException("Could not deserialize instances from this source."); } // close the stream oi.close(); } /** * Determines and returns (if possible) the structure (internally the * header) of the data set as an empty set of instances. * * @return the structure of the data set as an empty set of Instances * @throws IOException if an error occurs */ public Instances getStructure() throws IOException { if (m_Dataset == null) { throw new IOException("No source has been specified"); } // We could cache a structure-only if getStructure is likely to be called // many times. return new Instances(m_Dataset, 0); } /** * Return the full data set. If the structure hasn't yet been determined * by a call to getStructure then method should do so before processing * the rest of the data set. * * @return the structure of the data set as an empty set of Instances * @throws IOException if there is no source or parsing fails */ public Instances getDataSet() throws IOException { if (m_Dataset == null) { throw new IOException("No source has been specified"); } return m_Dataset; } /** * Read the data set incrementally---get the next instance in the data * set or returns null if there are no * more instances to get. If the structure hasn't yet been * determined by a call to getStructure then method should do so before * returning the next instance in the data set. * * @param structure ignored * @return the next instance in the data set as an Instance object or null * if there are no more instances to be read * @throws IOException if there is an error during parsing */ public Instance getNextInstance(Instances structure) throws IOException { if (m_Dataset == null) { throw new IOException("No source has been specified"); } // We have to fake this method, since we can only deserialize an entire // dataset at a time. if (m_IncrementalIndex == m_Dataset.numInstances()) { return null; } return m_Dataset.instance(m_IncrementalIndex++); } /** * Returns the revision string. * * @return the revision */ public String getRevision() { return RevisionUtils.extract("$Revision$"); } /** * Main method. * * @param args should contain the name of an input file. */ public static void main(String[] args) { runFileLoader(new SerializedInstancesLoader(), args); } }