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package java.util;

import java.lang.*;


The string tokenizer class allows an application to break a string into tokens. The tokenization method is much simpler than the one used by the StreamTokenizer class. The StringTokenizer methods do not distinguish among identifiers, numbers, and quoted strings, nor do they recognize and skip comments. 

The set of delimiters (the characters that separate tokens) may
be specified either at creation time or on a per-token basis.

 An instance of StringTokenizer behaves in one of two ways, depending on whether it was created with the returnDelims flag having the value true or false: 
    

  • If the flag is false, delimiter characters serve to separate tokens. A token is a maximal sequence of consecutive characters that are not delimiters. 
  • If the flag is true, delimiter characters are themselves considered to be tokens. A token is thus either one delimiter character, or a maximal sequence of consecutive characters that are not delimiters. 
 A StringTokenizer object internally maintains a current position within the string to be tokenized. Some operations advance this current position past the characters processed.
 A token is returned by taking a substring of the string that was used to create the StringTokenizer object. 

The following is one example of the use of the tokenizer. The code:

    StringTokenizer st = new StringTokenizer("this is a test");
    while (st.hasMoreTokens()) {
        System.out.println(st.nextToken());
    }




prints the following output:

    this
    is
    a
    test



 StringTokenizer is a legacy class that is retained for compatibility reasons although its use is discouraged in new code. It is recommended that anyone seeking this functionality use the split method of String or the java.util.regex package instead. 
 The following example illustrates how the String.split method can be used to break up a string into its basic tokens: 
    String[] result = "this is a test".split("\\s");
    for (int x=0; x<result.length; x++)
        System.out.println(result[x]);




prints the following output:

    this
    is
    a
    test



Author: unascribed
See Also:
Since:  1.0
/**
 * The string tokenizer class allows an application to break a
 * string into tokens. The tokenization method is much simpler than
 * the one used by the {@code StreamTokenizer} class. The
 * {@code StringTokenizer} methods do not distinguish among
 * identifiers, numbers, and quoted strings, nor do they recognize
 * and skip comments.
 * <p>
 * The set of delimiters (the characters that separate tokens) may
 * be specified either at creation time or on a per-token basis.
 * <p>
 * An instance of {@code StringTokenizer} behaves in one of two
 * ways, depending on whether it was created with the
 * {@code returnDelims} flag having the value {@code true}
 * or {@code false}:
 * <ul>
 * <li>If the flag is {@code false}, delimiter characters serve to
 *     separate tokens. A token is a maximal sequence of consecutive
 *     characters that are not delimiters.
 * <li>If the flag is {@code true}, delimiter characters are themselves
 *     considered to be tokens. A token is thus either one delimiter
 *     character, or a maximal sequence of consecutive characters that are
 *     not delimiters.
 * </ul><p>
 * A {@code StringTokenizer} object internally maintains a current
 * position within the string to be tokenized. Some operations advance this
 * current position past the characters processed.<p>
 * A token is returned by taking a substring of the string that was used to
 * create the {@code StringTokenizer} object.
 * <p>
 * The following is one example of the use of the tokenizer. The code:
 * <blockquote><pre>
 *     StringTokenizer st = new StringTokenizer("this is a test");
 *     while (st.hasMoreTokens()) {
 *         System.out.println(st.nextToken());
 *     }
 * </pre></blockquote>
 * <p>
 * prints the following output:
 * <blockquote><pre>
 *     this
 *     is
 *     a
 *     test
 * </pre></blockquote>
 *
 * <p>
 * {@code StringTokenizer} is a legacy class that is retained for
 * compatibility reasons although its use is discouraged in new code. It is
 * recommended that anyone seeking this functionality use the {@code split}
 * method of {@code String} or the java.util.regex package instead.
 * <p>
 * The following example illustrates how the {@code String.split}
 * method can be used to break up a string into its basic tokens:
 * <blockquote><pre>
 *     String[] result = "this is a test".split("\\s");
 *     for (int x=0; x&lt;result.length; x++)
 *         System.out.println(result[x]);
 * </pre></blockquote>
 * <p>
 * prints the following output:
 * <blockquote><pre>
 *     this
 *     is
 *     a
 *     test
 * </pre></blockquote>
 *
 * @author  unascribed
 * @see     java.io.StreamTokenizer
 * @since   1.0
 */
public
class StringTokenizer implements Enumeration<Object> {
    private int currentPosition;
    private int newPosition;
    private int maxPosition;
    private String str;
    private String delimiters;
    private boolean retDelims;
    private boolean delimsChanged;

    
maxDelimCodePoint stores the value of the delimiter character with the
highest value. It is used to optimize the detection of delimiter
characters.
It is unlikely to provide any optimization benefit in the
hasSurrogates case because most string characters will be
smaller than the limit, but we keep it so that the two code
paths remain similar.

/**
     * maxDelimCodePoint stores the value of the delimiter character with the
     * highest value. It is used to optimize the detection of delimiter
     * characters.
     *
     * It is unlikely to provide any optimization benefit in the
     * hasSurrogates case because most string characters will be
     * smaller than the limit, but we keep it so that the two code
     * paths remain similar.
     */
    private int maxDelimCodePoint;

    
If delimiters include any surrogates (including surrogate
pairs), hasSurrogates is true and the tokenizer uses the
different code path. This is because String.indexOf(int)
doesn't handle unpaired surrogates as a single character.

/**
     * If delimiters include any surrogates (including surrogate
     * pairs), hasSurrogates is true and the tokenizer uses the
     * different code path. This is because String.indexOf(int)
     * doesn't handle unpaired surrogates as a single character.
     */
    private boolean hasSurrogates = false;

    
When hasSurrogates is true, delimiters are converted to code
points and isDelimiter(int) is used to determine if the given
codepoint is a delimiter.

/**
     * When hasSurrogates is true, delimiters are converted to code
     * points and isDelimiter(int) is used to determine if the given
     * codepoint is a delimiter.
     */
    private int[] delimiterCodePoints;

    
Set maxDelimCodePoint to the highest char in the delimiter set.

/**
     * Set maxDelimCodePoint to the highest char in the delimiter set.
     */
    private void setMaxDelimCodePoint() {
        if (delimiters == null) {
            maxDelimCodePoint = 0;
            return;
        }

        int m = 0;
        int c;
        int count = 0;
        for (int i = 0; i < delimiters.length(); i += Character.charCount(c)) {
            c = delimiters.charAt(i);
            if (c >= Character.MIN_HIGH_SURROGATE && c <= Character.MAX_LOW_SURROGATE) {
                c = delimiters.codePointAt(i);
                hasSurrogates = true;
            }
            if (m < c)
                m = c;
            count++;
        }
        maxDelimCodePoint = m;

        if (hasSurrogates) {
            delimiterCodePoints = new int[count];
            for (int i = 0, j = 0; i < count; i++, j += Character.charCount(c)) {
                c = delimiters.codePointAt(j);
                delimiterCodePoints[i] = c;
            }
        }
    }

    
Constructs a string tokenizer for the specified string. All characters in the delim argument are the delimiters for separating tokens. 
 If the returnDelims flag is true, then the delimiter characters are also returned as tokens. Each delimiter is returned as a string of length one. If the flag is false, the delimiter characters are skipped and only serve as separators between tokens. 
 Note that if delim is null, this constructor does not throw an exception. However, trying to invoke other methods on the resulting StringTokenizer may result in a NullPointerException. 
Params:
  • str –            a string to be parsed.
  • delim –          the delimiters.
  • returnDelims –   flag indicating whether to return the delimiters
                        as tokens.
Throws:
/**
     * Constructs a string tokenizer for the specified string. All
     * characters in the {@code delim} argument are the delimiters
     * for separating tokens.
     * <p>
     * If the {@code returnDelims} flag is {@code true}, then
     * the delimiter characters are also returned as tokens. Each
     * delimiter is returned as a string of length one. If the flag is
     * {@code false}, the delimiter characters are skipped and only
     * serve as separators between tokens.
     * <p>
     * Note that if {@code delim} is {@code null}, this constructor does
     * not throw an exception. However, trying to invoke other methods on the
     * resulting {@code StringTokenizer} may result in a
     * {@code NullPointerException}.
     *
     * @param   str            a string to be parsed.
     * @param   delim          the delimiters.
     * @param   returnDelims   flag indicating whether to return the delimiters
     *                         as tokens.
     * @exception NullPointerException if str is {@code null}
     */
    public StringTokenizer(String str, String delim, boolean returnDelims) {
        currentPosition = 0;
        newPosition = -1;
        delimsChanged = false;
        this.str = str;
        maxPosition = str.length();
        delimiters = delim;
        retDelims = returnDelims;
        setMaxDelimCodePoint();
    }

    
Constructs a string tokenizer for the specified string. The characters in the delim argument are the delimiters for separating tokens. Delimiter characters themselves will not be treated as tokens. 
 Note that if delim is null, this constructor does not throw an exception. However, trying to invoke other methods on the resulting StringTokenizer may result in a NullPointerException. 
Params:
  • str –     a string to be parsed.
  • delim –   the delimiters.
Throws:
/**
     * Constructs a string tokenizer for the specified string. The
     * characters in the {@code delim} argument are the delimiters
     * for separating tokens. Delimiter characters themselves will not
     * be treated as tokens.
     * <p>
     * Note that if {@code delim} is {@code null}, this constructor does
     * not throw an exception. However, trying to invoke other methods on the
     * resulting {@code StringTokenizer} may result in a
     * {@code NullPointerException}.
     *
     * @param   str     a string to be parsed.
     * @param   delim   the delimiters.
     * @exception NullPointerException if str is {@code null}
     */
    public StringTokenizer(String str, String delim) {
        this(str, delim, false);
    }

    
Constructs a string tokenizer for the specified string. The
tokenizer uses the default delimiter set, which is
" \t\n\r\f": the space character,
the tab character, the newline character, the carriage-return character,
and the form-feed character. Delimiter characters themselves will
not be treated as tokens.

Params:
  • str –   a string to be parsed.
Throws:
/**
     * Constructs a string tokenizer for the specified string. The
     * tokenizer uses the default delimiter set, which is
     * <code>"&nbsp;&#92;t&#92;n&#92;r&#92;f"</code>: the space character,
     * the tab character, the newline character, the carriage-return character,
     * and the form-feed character. Delimiter characters themselves will
     * not be treated as tokens.
     *
     * @param   str   a string to be parsed.
     * @exception NullPointerException if str is {@code null}
     */
    public StringTokenizer(String str) {
        this(str, " \t\n\r\f", false);
    }

    
Skips delimiters starting from the specified position. If retDelims
is false, returns the index of the first non-delimiter character at or
after startPos. If retDelims is true, startPos is returned.

/**
     * Skips delimiters starting from the specified position. If retDelims
     * is false, returns the index of the first non-delimiter character at or
     * after startPos. If retDelims is true, startPos is returned.
     */
    private int skipDelimiters(int startPos) {
        if (delimiters == null)
            throw new NullPointerException();

        int position = startPos;
        while (!retDelims && position < maxPosition) {
            if (!hasSurrogates) {
                char c = str.charAt(position);
                if ((c > maxDelimCodePoint) || (delimiters.indexOf(c) < 0))
                    break;
                position++;
            } else {
                int c = str.codePointAt(position);
                if ((c > maxDelimCodePoint) || !isDelimiter(c)) {
                    break;
                }
                position += Character.charCount(c);
            }
        }
        return position;
    }

    
Skips ahead from startPos and returns the index of the next delimiter
character encountered, or maxPosition if no such delimiter is found.

/**
     * Skips ahead from startPos and returns the index of the next delimiter
     * character encountered, or maxPosition if no such delimiter is found.
     */
    private int scanToken(int startPos) {
        int position = startPos;
        while (position < maxPosition) {
            if (!hasSurrogates) {
                char c = str.charAt(position);
                if ((c <= maxDelimCodePoint) && (delimiters.indexOf(c) >= 0))
                    break;
                position++;
            } else {
                int c = str.codePointAt(position);
                if ((c <= maxDelimCodePoint) && isDelimiter(c))
                    break;
                position += Character.charCount(c);
            }
        }
        if (retDelims && (startPos == position)) {
            if (!hasSurrogates) {
                char c = str.charAt(position);
                if ((c <= maxDelimCodePoint) && (delimiters.indexOf(c) >= 0))
                    position++;
            } else {
                int c = str.codePointAt(position);
                if ((c <= maxDelimCodePoint) && isDelimiter(c))
                    position += Character.charCount(c);
            }
        }
        return position;
    }

    private boolean isDelimiter(int codePoint) {
        for (int delimiterCodePoint : delimiterCodePoints) {
            if (delimiterCodePoint == codePoint) {
                return true;
            }
        }
        return false;
    }

    
Tests if there are more tokens available from this tokenizer's string. If this method returns true, then a subsequent call to nextToken with no argument will successfully return a token. 
Returns: true if and only if there is at least one token in the string after the current position; false otherwise.
/**
     * Tests if there are more tokens available from this tokenizer's string.
     * If this method returns {@code true}, then a subsequent call to
     * {@code nextToken} with no argument will successfully return a token.
     *
     * @return  {@code true} if and only if there is at least one token
     *          in the string after the current position; {@code false}
     *          otherwise.
     */
    public boolean hasMoreTokens() {
        /*
         * Temporarily store this position and use it in the following
         * nextToken() method only if the delimiters haven't been changed in
         * that nextToken() invocation.
         */
        newPosition = skipDelimiters(currentPosition);
        return (newPosition < maxPosition);
    }

    
Returns the next token from this string tokenizer.

Throws:
Returns:    the next token from this string tokenizer.
/**
     * Returns the next token from this string tokenizer.
     *
     * @return     the next token from this string tokenizer.
     * @exception  NoSuchElementException  if there are no more tokens in this
     *               tokenizer's string.
     */
    public String nextToken() {
        /*
         * If next position already computed in hasMoreElements() and
         * delimiters have changed between the computation and this invocation,
         * then use the computed value.
         */

        currentPosition = (newPosition >= 0 && !delimsChanged) ?
            newPosition : skipDelimiters(currentPosition);

        /* Reset these anyway */
        delimsChanged = false;
        newPosition = -1;

        if (currentPosition >= maxPosition)
            throw new NoSuchElementException();
        int start = currentPosition;
        currentPosition = scanToken(currentPosition);
        return str.substring(start, currentPosition);
    }

    
Returns the next token in this string tokenizer's string. First, the set of characters considered to be delimiters by this StringTokenizer object is changed to be the characters in the string delim. Then the next token in the string after the current position is returned. The current position is advanced beyond the recognized token. The new delimiter set remains the default after this call. 
Params:
  • delim –   the new delimiters.
Throws:
Returns:    the next token, after switching to the new delimiter set.
/**
     * Returns the next token in this string tokenizer's string. First,
     * the set of characters considered to be delimiters by this
     * {@code StringTokenizer} object is changed to be the characters in
     * the string {@code delim}. Then the next token in the string
     * after the current position is returned. The current position is
     * advanced beyond the recognized token.  The new delimiter set
     * remains the default after this call.
     *
     * @param      delim   the new delimiters.
     * @return     the next token, after switching to the new delimiter set.
     * @exception  NoSuchElementException  if there are no more tokens in this
     *               tokenizer's string.
     * @exception NullPointerException if delim is {@code null}
     */
    public String nextToken(String delim) {
        delimiters = delim;

        /* delimiter string specified, so set the appropriate flag. */
        delimsChanged = true;

        setMaxDelimCodePoint();
        return nextToken();
    }

    
Returns the same value as the hasMoreTokens method. It exists so that this class can implement the Enumeration interface. 
See Also:
Returns: true if there are more tokens; false otherwise.
/**
     * Returns the same value as the {@code hasMoreTokens}
     * method. It exists so that this class can implement the
     * {@code Enumeration} interface.
     *
     * @return  {@code true} if there are more tokens;
     *          {@code false} otherwise.
     * @see     java.util.Enumeration
     * @see     java.util.StringTokenizer#hasMoreTokens()
     */
    public boolean hasMoreElements() {
        return hasMoreTokens();
    }

    
Returns the same value as the nextToken method, except that its declared return value is Object rather than String. It exists so that this class can implement the Enumeration interface. 
Throws:
See Also:
Returns:    the next token in the string.
/**
     * Returns the same value as the {@code nextToken} method,
     * except that its declared return value is {@code Object} rather than
     * {@code String}. It exists so that this class can implement the
     * {@code Enumeration} interface.
     *
     * @return     the next token in the string.
     * @exception  NoSuchElementException  if there are no more tokens in this
     *               tokenizer's string.
     * @see        java.util.Enumeration
     * @see        java.util.StringTokenizer#nextToken()
     */
    public Object nextElement() {
        return nextToken();
    }

    
Calculates the number of times that this tokenizer's nextToken method can be called before it generates an exception. The current position is not advanced. 
See Also:
Returns: the number of tokens remaining in the string using the current
         delimiter set.
/**
     * Calculates the number of times that this tokenizer's
     * {@code nextToken} method can be called before it generates an
     * exception. The current position is not advanced.
     *
     * @return  the number of tokens remaining in the string using the current
     *          delimiter set.
     * @see     java.util.StringTokenizer#nextToken()
     */
    public int countTokens() {
        int count = 0;
        int currpos = currentPosition;
        while (currpos < maxPosition) {
            currpos = skipDelimiters(currpos);
            if (currpos >= maxPosition)
                break;
            currpos = scanToken(currpos);
            count++;
        }
        return count;
    }
}