fileparser.java

一个决策树的Applet（转载

package ai.decision.algorithm;

import java.io.*;
import java.util.*;

/**
 * The FileParser class contains methods that are used to
 * parse decision tree metadata and example files.
 *
 * <p>
 * Metadata files have the following format:
 *
 * <p><pre>
 *
 * &lt;infofile&gt; :==  CONCLUSION =
 *                    &lt;feature&gt;
 *
 *                   FEATURES =
 *                      &lt;feature&gt;,
 *                      ...
 *
 *                   TRAINDATA = &quot;&lt;string&gt;&quot;
 *
 *  &lt;feature&gt; :==  &quot;&lt;string&gt;&quot;
 *                       = { '&lt;string&gt;', ... }
 * </pre>
 *
 * <p>
 * Data files have the following format:
 *
 * <p><pre>
 * &lt;datafile&gt; :== &lt;featureset&gt; \n ...
 *
 * &lt;featureset&gt; :== &lt;string&gt;,...
 * </pre>
 *
 * <p>
 * <b>Change History:</b>
 *
 * <p><pre>
 * Name:            Date:            Change:
 * =============================================================
 * J. Kelly         May-04-2000      Created.
 * </pre>
 *
 * Copyright 2000 University of Alberta.
 *
 * <!--
 * This file is part of the Decision Tree Applet.
 *
 * The Decision Tree Applet 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.
 *
 * Foobar 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 the Decision Tree Applet; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * -->
 */
public class FileParser
{
  // Instance data members

  LineNumberReader m_lineReader;  // Reads file line-by-line.
  String           m_fileText;    // Text buffer.
  boolean          m_openBracket; // Indicates an open bracket
                                  // has been parsed - used as an
                                  // identifier.

  boolean m_attributeDomain;  // Indicates that the next
                              // item to be parsed is an
                              // attribute domain.
  boolean m_attributesRemain; // Indicates that there are
                              // remaining attributes to
                              // be parsed in this section of
                              // of the file.

  // Constructors

  /**
   * Creates a new FileParser.
   */
  public FileParser()
  {}

  // Public methods

  /**
   * Opens the specified configuration file and prepares
   * it for parsing by reading it into memory.
   *
   * @param metaInputStream A stream attached to the metadata
   *        file for a given data set.
   *
   * @throws IOException If a problem occurs while reading
   *         the configuration file.
   */
  public void startMetaParse( InputStream metaInputStream )
    throws IOException
  {
    // Try to create a new line reader.
    m_lineReader = new LineNumberReader(
    new InputStreamReader( metaInputStream ) );

    // Since the configuration files are small (generally) and
    // need to be parsed, we read the entire file at once and
    // concatenate the text into one long string.

    // At some point, we should use a more robust parsing system.
    StringBuffer tempFileText = new StringBuffer();
    String       tempLine = null;

    while( (tempLine = m_lineReader.readLine()) != null )
      tempFileText.append( tempLine );

    m_fileText = tempFileText.toString();
    m_lineReader = null;
  }

  /**
   * Opens the specified data file and prepares it for
   * parsing.  Data files are read one line at a time.
   *
   * @param dataInputStream A stream attached to the data file
   *        for a given dataset.
   *
   * @throws IOException If a problem occurs while
   *         opening the data file.
   */
  public void startDataParse( InputStream dataInputStream )
    throws IOException
  {
    // Try to open the data file.
    m_lineReader = new LineNumberReader(
      new InputStreamReader( dataInputStream ) );

    // Data files (which can be extremely long) are read
    // and parsed one line at a time.
  }

  /**
   * Moves through the configuration file data (stored in
   * memory) to the position where the target attribute
   * name should be located.
   *
   * @throws InvalidMetaFileException If a syntax
   *         error is found.
   */
  public void moveToTargetAttribute()
    throws InvalidMetaFileException
  {
    stripString( "CONCLUSION" );
    m_attributesRemain = true;
  }

  /**
   * Moves through the configuration file data (stored in
   * memory) to the position where the general attribute
   * information should be located.
   *
   * @throws InvalidMetaFileException If a syntax
   *         error is found.
   */
  public void moveToAttributes()
    throws InvalidMetaFileException
  {
    stripString( "FEATURES" );
    m_attributesRemain = true;
  }

  /**
   * Moves through the configuration file (stored in
   * memory) to the position where the training data file
   * path should be located.
   *
   * @throws InvalidMetaFileException if a syntax
   *         error is found.
   */
  public void moveToDataFilePath()
    throws InvalidMetaFileException
  {
    stripString( "TRAINDATA" );
  }

  /**
   * Returns the character string between the first pair of
   * double quotes.  The method checks for and removes the quotes,
   * any characters between the quotes, and the '=' sign that
   * follows the quotes.
   *
   * @return A String containing the name of the attribute that is
   *         extracted.
   *
   * @throws InvalidMetaFileException If a syntax error is
   *         found.
   */
  public String extractAttributeName()
    throws InvalidMetaFileException
  {
    // Have we already finished parsing all attribute names?
    if( !m_attributesRemain ) return null;

    // Attribute names are enclosed in double-quotes.
    String attributeName = extractString( '\"', '\"', true );

    // Strip the '=' sign after the quoted attribute name.
    if( !stripCharacter( '=' ) )
      throw new
        InvalidMetaFileException( "Syntax error in " +
          "configuration file: No '=' sign after attribute name." );

    // Set the attribute domain flag to indicate that
    // the next thing we should be looking to parse
    // is a set of attribute values.
    m_attributeDomain = true;

    return attributeName;
  }

  /**
   * Returns the character string between the first pair of
   * single quotes. The method checks for and removes the quotes,
   * any characters between the quotes, and any curly brace
   * delimiters.
   *
   * @return A String containing the name of the next
   *         attribute value, or null if there are no
   *         more attribute values.
   */
  public String extractAttributeValue()
    throws InvalidMetaFileException
  {
    // Have we already finished parsing values?
    if( !m_attributeDomain ) return null;

    // Have we started parsing values yet?
    // (i.e. have we stripped out the initial curly brace?)
    if( !m_openBracket ) {
      if( !stripCharacter( '{' ) )
        throw new
          InvalidMetaFileException( "Syntax error " +
            "in configuration file: Missing '{' before attribute values." );

      m_openBracket = true;
    }

    // Extract the value name from the file text.
    String valueName = extractString( '\'', '\'', true );

    // Strip the ',' after the quoted value name.  If
    // there's no ',' character, then look for the closing curly brace.
    if( !stripCharacter( ',' ) ) {
      if( !stripCharacter( '}' ) )
        throw new
          InvalidMetaFileException( "Syntax error in " +
            "configuration file: No ',' or '}' after attribute name." );
      else {
        m_openBracket     = false;  // bracket matched
        m_attributeDomain = false;  // finished this domain

        if( !stripCharacter( ',' ) )
          // There are no more attributes to parse.
          m_attributesRemain = false;
      }
    }

    return valueName;
  }

  /**
   * Extracts and returns a string from the current
   * file text.  Double-quote characters are used as
   * delimeters.  The string and the quotes are removed
   * from the file text.
   *