libjava/java/util/StringTokenizer.java

/* java.util.StringTokenizer
   Copyright (C) 1998, 1999, 2001 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath 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, or (at your option)
any later version.

GNU Classpath 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 GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

As a special exception, if you link this library with other files to
produce an executable, this library does not by itself cause the
resulting executable to be covered by the GNU General Public License.
This exception does not however invalidate any other reasons why the
executable file might be covered by the GNU General Public License. */


package java.util;

/**
 * This class splits a string into tokens.  The caller can set on which 
 * delimiters the string should be split and if the delimiters should be
 * returned.
 *
 * You may change the delimiter set on the fly by calling
 * nextToken(String).  But the semantic is quite difficult; it even
 * depends on calling <code>hasMoreTokens()</code>.  You should call
 * <code>hasMoreTokens()</code> before, otherwise the old delimiters
 * after the last token are returned.
 *
 * If you want to get the delimiters, you have to use the three argument
 * constructor.  The delimiters are returned as token consisting of a
 * single character.  
 *
 * @author Jochen Hoenicke
 * @author Warren Levy <warrenl@cygnus.com>
 */
public class StringTokenizer implements Enumeration
{
  /**
   * The position in the str, where we currently are.
   */
  private int pos;
  /**
   * The string that should be split into tokens.
   */
  private String str;
  /**
   * The string containing the delimiter characters.
   */
  private String delim;
  /**
   * Tells, if we should return the delimiters.
   */
  private boolean retDelims;

  /*{ 
     invariant {
     pos >= 0 :: "position is negative";
     pos <= str.length() :: "position is out of string";
     str != null :: "String is null";
     delim != null :: "Delimiters are null";
     }
     } */

  /**
   * Creates a new StringTokenizer for the string <code>str</code>,
   * that should split on the default delimiter set (space, tap,
   * newline, return and formfeed), and which doesn't return the
   * delimiters.
   * @param str The string to split.
   */
  public StringTokenizer(String str)
    /*{ require { str != null :: "str must not be null"; } } */
  {
    this(str, " \t\n\r\f", false);
  }

  /**
   * Create a new StringTokenizer, that splits the given string on 
   * the given delimiter characters.  It doesn't return the delimiter
   * characters.
   *
   * @param str The string to split.
   * @param delim A string containing all delimiter characters.
   */
  public StringTokenizer(String str, String delim)
    /*{ require { str != null :: "str must not be null";
       delim != null :: "delim must not be null"; } } */
  {
    this(str, delim, false);
  }

  /**
   * Create a new StringTokenizer, that splits the given string on
   * the given delimiter characters.  If you set
   * <code>returnDelims</code> to <code>true</code>, the delimiter
   * characters are returned as tokens of their own.  The delimiter
   * tokens always consist of a single character.
   *
   * @param str The string to split.
   * @param delim A string containing all delimiter characters.
   * @param returnDelims Tells, if you want to get the delimiters.
   */
  public StringTokenizer(String str, String delim, boolean returnDelims)
    /*{ require { str != null :: "str must not be null";
       delim != null :: "delim must not be null"; } } */
  {
    this.str = str;
    this.delim = delim;
    this.retDelims = returnDelims;
    this.pos = 0;
  }

  /**
   * Tells if there are more tokens.
   * @return True, if the next call of nextToken() succeeds, false otherwise.
   */
  public boolean hasMoreTokens()
  {
    if (!retDelims)
      {
	while (pos < str.length() && delim.indexOf(str.charAt(pos)) > -1)
	  {
	    pos++;
	  }
      }
    return pos < str.length();
  }

  /**
   * Returns the nextToken, changing the delimiter set to the given
   * <code>delim</code>.  The change of the delimiter set is
   * permanent, ie. the next call of nextToken(), uses the same
   * delimiter set.
   * @param delim a string containing the new delimiter characters.
   * @return the next token with respect to the new delimiter characters.
   * @exception NoSuchElementException if there are no more tokens.
   */
  public String nextToken(String delim) throws NoSuchElementException
    /*{ require { hasMoreTokens() :: "no more Tokens available";
       ensure { $return != null && $return.length() > 0; } } */
  {
    this.delim = delim;
    return nextToken();
  }

  /**
   * Returns the nextToken of the string.
   * @param delim a string containing the new delimiter characters.
   * @return the next token with respect to the new delimiter characters.
   * @exception NoSuchElementException if there are no more tokens.
   */
  public String nextToken() throws NoSuchElementException
    /*{ require { hasMoreTokens() :: "no more Tokens available";
       ensure { $return != null && $return.length() > 0; } } */
  {
    if (pos < str.length() && delim.indexOf(str.charAt(pos)) > -1)
      {
	if (retDelims)
	  return str.substring(pos, ++pos);

	while (++pos < str.length() && delim.indexOf(str.charAt(pos)) > -1)
	  {
	    /* empty */
	  }
      }
    if (pos < str.length())
      {
	int start = pos;
	while (++pos < str.length() && delim.indexOf(str.charAt(pos)) == -1)
	  {
	    /* empty */
	  }
	return str.substring(start, pos);
      }
    throw new NoSuchElementException();
  }

  /**
   * This does the same as hasMoreTokens. This is the
   * <code>Enumeration</code interface method.
   * @return True, if the next call of nextElement() succeeds, false
   * otherwise.  
   * @see #hasMoreTokens
   */
  public boolean hasMoreElements()
  {
    return hasMoreTokens();
  }

  /**
   * This does the same as nextTokens. This is the
   * <code>Enumeration</code interface method.
   * @return the next token with respect to the new delimiter characters.
   * @exception NoSuchElementException if there are no more tokens.
   * @see #nextToken
   */
  public Object nextElement() throws NoSuchElementException
  {
    return nextToken();
  }

  /**
   * This counts the number of remaining tokens in the string, with
   * respect to the current delimiter set.
   * @return the number of times <code>nextTokens()</code> will
   * succeed.  
   * @see #nextToken
   */
  public int countTokens()
  {
    int count = 0;
    int delimiterCount = 0;
    boolean tokenFound = false;		// Set when a non-delimiter is found
    int tmpPos = pos;

    // Note for efficiency, we count up the delimiters rather than check
    // retDelims every time we encounter one.  That way, we can
    // just do the conditional once at the end of the method
    while (tmpPos < str.length())
      {
	if (delim.indexOf(str.charAt(tmpPos++)) > -1)
	  {
	    if (tokenFound)
	      {
		// Got to the end of a token
	        count++;
	        tokenFound = false;
	      }

	    delimiterCount++;		// Increment for this delimiter
	  }
	else
	  {
	    tokenFound = true;

	    // Get to the end of the token
	    while (tmpPos < str.length()
		   && delim.indexOf(str.charAt(tmpPos)) == -1)
	      ++tmpPos;
	  }
      }

    // Make sure to count the last token 
    if (tokenFound)
      count++;

    // if counting delmiters add them into the token count
    return retDelims ? count + delimiterCount : count;
  }
}