content: // ===============================================================================
  // Authors: AFRL/RQQD
  // Organization: Air Force Research Laboratory, Aerospace Systems Directorate, Power and Control Division
  // 
  // Copyright (c) 2017 Government of the United State of America, as represented by
  // the Secretary of the Air Force.  No copyright is claimed in the United States under
  // Title 17, U.S. Code.  All Other Rights Reserved.
  // ===============================================================================
  
  /*
   * GRAL: GRAphing Library for Java(R)
   *
   * (C) Copyright 2009-2013 Erich Seifert <dev[at]erichseifert.de>,
   * Michael Seifert <mseifert[at]error-reports.org>
   *
   * This file is part of GRAL.
   *
   * GRAL 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 3 of the License, or
   * (at your option) any later version.
   *
   * GRAL 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.
   *
   * You should have received a copy of the GNU Lesser General Public License
   * along with GRAL.  If not, see <http://www.gnu.org/licenses/>.
   */
  package de.erichseifert.gral.data.statistics;
  
  import java.io.IOException;
  import java.io.ObjectInputStream;
  
  import de.erichseifert.gral.data.AbstractDataSource;
  import de.erichseifert.gral.data.DataChangeEvent;
  import de.erichseifert.gral.data.DataListener;
  import de.erichseifert.gral.data.DataSource;
  
  /**
   * Abstract base class for histograms. Derived classes must
   * make sure the {@code getColumnTypes()} method returns a correct array
   * with column types.
   * @see AbstractDataSource#setColumnTypes(Class...)
   */
  public abstract class Histogram extends AbstractDataSource
  		implements DataListener {
  	/** Version id for serialization. */
  	private static final long serialVersionUID = 5031290498142366257L;
  
  	/** Data source that is used to build the histogram. */
  	private final DataSource data;
  
  	/**
  	 * Initializes a new histograms with a data source.
  	 * @param data Data source to be analyzed.
  	 */
  	@SuppressWarnings("unchecked")
  	public Histogram(DataSource data) {
  		this.data = data;
  		this.data.addDataListener(this);
  	}
  
  	/**
  	 * Recalculates the histogram values.
  	 */
  	protected abstract void rebuildCells();
  
  	/**
  	 * Method that is invoked when data has been added.
  	 * This method is invoked by objects that provide support for
  	 * {@code DataListener}s and should not be called manually.
  	 * @param source Data source that has been changed.
  	 * @param events Optional event object describing the data values that
  	 *        have been added.
  	 */
  	public void dataAdded(DataSource source, DataChangeEvent... events) {
  		dataChanged(source, events);
  		notifyDataAdded(events);
  	}
  
  	/**
  	 * Method that is invoked when data has been updated.
  	 * This method is invoked by objects that provide support for
  	 * {@code DataListener}s and should not be called manually.
  	 * @param source Data source that has been changed.
  	 * @param events Optional event object describing the data values that
  	 *        have been updated.
  	 */
  	public void dataUpdated(DataSource source, DataChangeEvent... events) {
  		dataChanged(source, events);
  		notifyDataUpdated(events);
  	}
  
  	/**
  	 * Method that is invoked when data has been removed.
  	 * This method is invoked by objects that provide support for
  	 * {@code DataListener}s and should not be called manually.
  	 * @param source Data source that has been changed.
  	 * @param events Optional event object describing the data values that
  	 *        have been removed.
  	 */
  	public void dataRemoved(DataSource source, DataChangeEvent... events) {
  		dataChanged(source, events);
  		notifyDataRemoved(events);
  	}
  
  	/**
  	 * Method that is invoked when data has been added, updated, or removed.
  	 * This method is invoked by objects that provide support for
  	 * {@code DataListener}s and should not be called manually.
  	 * @param source Data source that has been changed.
  	 * @param events Optional event object describing the data values that
  	 *        have been changed.
  	 */
  	private void dataChanged(DataSource source, DataChangeEvent... events) {
  		rebuildCells();
  	}
  
  	/**
  	 * Returns the data source associated to this histogram.
  	 * @return Data source
  	 */
  	public DataSource getData() {
  		return data;
  	}
  
  	/**
  	 * Custom deserialization method.
  	 * @param in Input stream.
  	 * @throws ClassNotFoundException if a serialized class doesn't exist anymore.
  	 * @throws IOException if there is an error while reading data from the
  	 *         input stream.
  	 */
  	private void readObject(ObjectInputStream in)
  			throws ClassNotFoundException, IOException {
  		// Normal deserialization
  		in.defaultReadObject();
  
  		// Restore listeners
  		data.addDataListener(this);
  	}
  }
  