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;
  
  import java.io.IOException;
  import java.io.ObjectInputStream;
  import java.util.ArrayList;
  import java.util.List;
  
  /**
   * <p>Abstract class that represents a view on several rows of a data source.
   * Implementations must implement the method {@code accept(Row)} which
   * decides whether a specific row should be contained in this filtered data
   * source.</p>
   *
   * <p>Example that keeps only every second row:</p>
   * <pre>
   * DataSource filtered = new RowSubset() {
   *     public boolean accept(Row row) {
   *         return row.getIndex()%2 == 0;
   *     }
   * };
   * </pre>
   */
  public abstract class RowSubset extends AbstractDataSource
  		implements DataListener {
  	/** Version id for serialization. */
  	private static final long serialVersionUID = -5396152732545986903L;
  
  	/** Original data source. */
  	private final DataSource original;
  	/** List of row indexes that are stored in this filtered data source. */
  	private transient List<Integer> accepted;
  
  	/**
  	 * Creates a new instance with the specified data source.
  	 * @param original DataSource to be filtered.
  	 */
  	@SuppressWarnings("unchecked")
  	public RowSubset(DataSource original) {
  		accepted = new ArrayList<Integer>();
  		this.original = original;
  		this.original.addDataListener(this);
  		dataUpdated(this.original);
  	}
  
  	@Override
  	public Row getRow(int row) {
  		int rowOrig = accepted.get(row);
  		return original.getRow(rowOrig);
  	}
  
  	/**
  	 * Returns the row with the specified index.
  	 * @param col index of the column to return
  	 * @param row index of the row to return
  	 * @return the specified value of the data cell
  	 */
  	public Comparable<?> get(int col, int row) {
  		int rowOrig = accepted.get(row);
  		return original.get(col, rowOrig);
  	}
  
  	@Override
  	public int getColumnCount() {
  		return original.getColumnCount();
  	}
  
  	/**
  	 * Returns the number of rows of the data source.
  	 * @return number of rows in the data source.
  	 */
  	public int getRowCount() {
  		return accepted.size();
  	}
  
  	@Override
  	public Class<? extends Comparable<?>>[] getColumnTypes() {
  		return original.getColumnTypes();
  	}
  
  	/**
  	 * 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 added
  	 */
  	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) {
  		update();
  	}
  
  	/**
  	 * Updates the list of accepted rows.
  	 */
  	private void update() {
  		accepted.clear();
  		for (int rowIndex = 0; rowIndex < original.getRowCount(); rowIndex++) {
  			Row row = original.getRow(rowIndex);
  			if (accept(row)) {
  				accepted.add(rowIndex);
  			}
  		}
  	}
  
  	/**
  	 * Tests whether the specified row is accepted by this DataSubset or not.
  	 * @param row Row to be tested.
  	 * @return True if the row should be kept.
  	 */
  	public abstract boolean accept(Row row);
  
  	/**
  	 * 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();
  
  		// Handle transient fields
  		accepted = new ArrayList<Integer>();
  
  		// Update caches
  		dataUpdated(original);
  
  		// Restore listeners
  		original.addDataListener(this);
  	}
  }
  