Class: java.util.StringTokenizer

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
Authors:
@author unascribed
See:
@see java.io.StreamTokenizer
Version:
@version 1.34, 05/05/04
Since:
@since JDK1.0

Inheritance

Superclass tree: Implements:

Methods

  • StringTokenizertop

    public StringTokenizer(String str)
    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.
    Parameters:
    @param str a string to be parsed.
    Exceptions:
    @exception NullPointerException if str is null
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  • StringTokenizertop

    public StringTokenizer(String str, String delim)
    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.

    Parameters:
    @param str a string to be parsed.
    @param delim the delimiters.
    Exceptions:
    @exception NullPointerException if str is null
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  • StringTokenizertop

    public StringTokenizer(String str, String delim, boolean returnDelims)
    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.

    Parameters:
    @param str a string to be parsed.
    @param delim the delimiters.
    @param returnDelims flag indicating whether to return the delimiters as tokens.
    Exceptions:
    @exception NullPointerException if str is null
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  • countTokenstop

    public int countTokens()
    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.
    Return:
    @return the number of tokens remaining in the string using the current delimiter set.
    See:
    @see java.util.StringTokenizer.nextToken()
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  • hasMoreElementstop

    public boolean hasMoreElements()
    Returns the same value as the hasMoreTokens method. It exists so that this class can implement the Enumeration interface.
    Return:
    @return true if there are more tokens; false otherwise.
    See:
    @see java.util.Enumeration
    @see java.util.StringTokenizer.hasMoreTokens()
    Specified by:
    hasMoreElements from Enumeration<Object>
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  • hasMoreTokenstop

    public boolean hasMoreTokens()
    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.
    Return:
    @return true if and only if there is at least one token in the string after the current position; false otherwise.
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  • isDelimitertop

    private boolean isDelimiter(int codePoint)
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  • nextElementtop

    public Object nextElement()
    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.
    Return:
    @return the next token in the string.
    Exceptions:
    @exception NoSuchElementException if there are no more tokens in this tokenizer's string.
    See:
    @see java.util.Enumeration
    @see java.util.StringTokenizer.nextToken()
    Specified by:
    nextElement from Enumeration<Object>
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  • nextTokentop

    public String nextToken()
    Returns the next token from this string tokenizer.
    Return:
    @return the next token from this string tokenizer.
    Exceptions:
    @exception NoSuchElementException if there are no more tokens in this tokenizer's string.
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  • nextTokentop

    public String nextToken(String delim)
    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.
    Parameters:
    @param delim the new delimiters.
    Return:
    @return the next token, after switching to the new delimiter set.
    Exceptions:
    @exception NoSuchElementException if there are no more tokens in this tokenizer's string.
    @exception NullPointerException if delim is null
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  • scanTokentop

    private int scanToken(int startPos)
    Skips ahead from startPos and returns the index of the next delimiter character encountered, or maxPosition if no such delimiter is found.
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  • setMaxDelimCodePointtop

    private void setMaxDelimCodePoint()
    Set maxDelimCodePoint to the highest char in the delimiter set.
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  • skipDelimiterstop

    private int skipDelimiters(int startPos)
    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.
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Fields

  • currentPosition

    private int currentPosition

  • delimiterCodePoints

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

  • delimiters

    private String delimiters

  • delimsChanged

    private boolean delimsChanged

  • hasSurrogates

    private boolean hasSurrogates
    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.

  • maxDelimCodePoint

    private int maxDelimCodePoint
    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.

  • maxPosition

    private int maxPosition

  • newPosition

    private int newPosition

  • retDelims

    private boolean retDelims

  • str

    private String str