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.data;
  
  import edu.cmu.tetrad.util.TetradSerializable;
  import java.io.ObjectStreamException;
  import java.util.regex.Pattern;
  
  /**
   * Type-safe enum of delimiter types for parsing data. DISCRETE is used in data
   * where every line starts a new field and every occurrence of a tab starts a
   * new field. SECTION_MARKER is replaces tabs by " *\t *". LAUNCH_TIME replaces
   * tabs by ",". Custom replaces tabs by a specified regular expression.
   *
   * @author Joseph Ramsey
   */
  public final class DelimiterType implements TetradSerializable {
  
      static final long serialVersionUID = 23L;
  
      public static final DelimiterType WHITESPACE
              = new DelimiterType("Whitespace", "\\s+");
      public static final DelimiterType TAB
              = new DelimiterType("Tab", "\t");
      public static final DelimiterType COMMA
              = new DelimiterType("Comma", ",");
      public static final DelimiterType COLON
              = new DelimiterType("Colon", ":");
  
      /**
       * The name of this type.
       */
      private transient final String name;
  
      /**
       * The regular expression representing the delimiter.
       */
      private transient final Pattern pattern;
  
      /**
       * Protected constructor for the types; this allows for extension in case
       * anyone wants to add formula types.
       */
      private DelimiterType(String name, String regex) {
          this.name = name;
          this.pattern = Pattern.compile(regex);
      }
  
      /**
       * Generates a simple exemplar of this class to test serialization.
       */
      public static DelimiterType serializableInstance() {
          return DelimiterType.TAB;
      }
  
      /**
       * @return the pattern representing this delimiter type. This pattern can be
       * used to parse, using a matcher.
       */
      public final Pattern getPattern() {
          return this.pattern;
      }
  
      /**
       * Prints out the name of the type.
       */
      public final String toString() {
          return name;
      }
  
      // Declarations required for serialization.
      private static int nextOrdinal = 0;
      private final int ordinal = nextOrdinal++;
      private static final DelimiterType[] TYPES = {WHITESPACE, TAB, COMMA};
  
      final Object readResolve() throws ObjectStreamException {
          return TYPES[ordinal]; // Canonicalize.
      }
  }
  