code: ///////////////////////////////////////////////////////////////////////////////
  // For information as to what this class does, see the Javadoc, below.       //
  // Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,       //
  // 2007, 2008, 2009, 2010, 2014, 2015 by Peter Spirtes, Richard Scheines, Joseph   //
  // Ramsey, and Clark Glymour.                                                //
  //                                                                           //
  // 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 2 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA //
  ///////////////////////////////////////////////////////////////////////////////
  
  package edu.pitt.isp.sverchkov.data;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  
  /**
   *
   * @author YUS24
   */
  public class DataTableImpl<N,V> implements DataTable<N,V> {
      
      private final List<N> variables;
      private final List<List<V>> rows;
      
      public DataTableImpl( List<? extends N> vars ){
          variables = Collections.unmodifiableList( new ArrayList<>( vars ) );
          rows = new ArrayList<>();
      }
  
      @Override
      public List<N> variables() {
          return variables;
      }
  
      @Override
      public int columnCount() {
          return variables.size();
      }
  
      @Override
      public int rowCount() {
          return rows.size();
      }
  
      @Override
      public void addRow(List<? extends V> row) {
          final int
                  m = row.size(),
                  w = columnCount();
          
          if( m != w )
              throw new IllegalArgumentException( "Tried to insert a row of length "+m+" into a table of width "+w+"." );
          
          rows.add( Collections.unmodifiableList( new ArrayList<>( row ) ) );
      }
  
      @Override
      public Iterator<List<V>> iterator() {
          return Collections.unmodifiableList( rows ).listIterator();
      }
      
  }
  
  