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.cmu.tetrad.gene.tetrad.gene.history;
  
  import edu.cmu.tetrad.util.TetradSerializable;
  
  import java.io.IOException;
  import java.io.ObjectInputStream;
  
  /**
   * wrapper class for passing factor+edge via a propertyChange event
   *
   * @author gmli
   */
  public class LaggedEdge implements TetradSerializable {
      static final long serialVersionUID = 23L;
  
      /**
       * @serial
       */
      private String factor;
  
      /**
       * @serial
       */
      private LaggedFactor laggedFactor;
  
      //==============================CONSTRUCTORS========================//
  
      /**
       * Creates new LaggedEdge
       */
      public LaggedEdge(String factor, LaggedFactor laggedFactor) {
          if (factor == null) {
              throw new NullPointerException("Edge name must not be null");
          }
  
          if (laggedFactor == null) {
              throw new NullPointerException("Lagged factor must not be null");
          }
  
          this.factor = factor;
          this.laggedFactor = laggedFactor;
      }
  
      /**
       * Generates a simple exemplar of this class to test serialization.
       *
       * @see edu.cmu.TestSerialization
       * @see edu.cmu.tetradapp.util.TetradSerializableUtils
       */
      public static LaggedEdge serializableInstance() {
          return new LaggedEdge("X", LaggedFactor.serializableInstance());
      }
  
      //=============================PUBLIC METHODS======================//
  
      public String getFactor() {
          return factor;
      }
  
      public LaggedFactor getLaggedFactor() {
          return laggedFactor;
      }
  
      /**
       * Adds semantic checks to the default deserialization method. This method
       * must have the standard signature for a readObject method, and the body of
       * the method must begin with "s.defaultReadObject();". Other than that, any
       * semantic checks can be specified and do not need to stay the same from
       * version to version. A readObject method of this form may be added to any
       * class, even if Tetrad sessions were previously saved out using a version
       * of the class that didn't include it. (That's what the
       * "s.defaultReadObject();" is for. See J. Bloch, Effective Java, for help.
       *
       * @throws java.io.IOException
       * @throws ClassNotFoundException
       */
      private void readObject(ObjectInputStream s)
              throws IOException, ClassNotFoundException {
          s.defaultReadObject();
  
          if (factor == null) {
              throw new NullPointerException();
          }
  
          if (laggedFactor == null) {
              throw new NullPointerException();
          }
  
      }
  }
  
  
  
  
  
  