java.util: public class: StringTokenizer

java.util
public class: StringTokenizer [javadoc | source]

java.lang.Object
   java.util.StringTokenizer

All Implemented Interfaces:
Enumeration

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

Also see:

java.io.StreamTokenizer

author: unascribed -

since: JDK1.0 -

Constructor:

Constructor:
public StringTokenizer(String str) { this(str, " \t\n\r\f", 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. Parameters: `str` - a string to be parsed. Throws: `NullPointerException` - if str is `null` exception: `NullPointerException` - if str is `null`
public StringTokenizer(String str, String delim) { this(str, delim, false); } 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: `str` - a string to be parsed. `delim` - the delimiters. Throws: `NullPointerException` - if str is `null` exception: `NullPointerException` - if str is `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. 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: `str` - a string to be parsed. `delim` - the delimiters. `returnDelims` - flag indicating whether to return the delimiters as tokens. Throws: `NullPointerException` - if str is `null` exception: `NullPointerException` - if str is `null`

 public StringTokenizer(String str) {
        this(str, " \t\n\r\f", false);
}

" \t\n\r\f"

Parameters:

str - a string to be parsed.

Throws:

NullPointerException - if str is null

exception: NullPointerException - if str is null

 public StringTokenizer(String str,
    String delim) {
        this(str, delim, false);
}

delim

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:

str - a string to be parsed.

delim - the delimiters.

Throws:

NullPointerException - if str is null

exception: NullPointerException - if str is 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();
}

delim

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:

str - a string to be parsed.

delim - the delimiters.

returnDelims - flag indicating whether to return the delimiters as tokens.

Throws:

NullPointerException - if str is null

exception: NullPointerException - if str is null

Method from java.util.StringTokenizer Summary:
countTokens, hasMoreElements, hasMoreTokens, nextElement, nextToken, nextToken

Methods from java.lang.Object:
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method from java.util.StringTokenizer Detail:
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; } 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.
public boolean hasMoreElements() { return hasMoreTokens(); } Returns the same value as the `hasMoreTokens` method. It exists so that this class can implement the `Enumeration` interface.
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); } 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.
public Object nextElement() { return nextToken(); } 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.
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 from this string tokenizer.
public String nextToken(String delim) { delimiters = delim; /* delimiter string specified, so set the appropriate flag. */ delimsChanged = true; setMaxDelimCodePoint(); return nextToken(); } 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.

Method from java.util.StringTokenizer Detail:

 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;
}

nextToken

 public boolean hasMoreElements() {
        return hasMoreTokens();
}

hasMoreTokens

Enumeration

 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);
}

true

nextToken

 public Object nextElement() {
        return nextToken();
}

nextToken

Object

String

Enumeration

 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 from this string tokenizer.

 public String nextToken(String delim) {
        delimiters = delim;
        /* delimiter string specified, so set the appropriate flag. */
        delimsChanged = true;
        setMaxDelimCodePoint();
        return nextToken();
}

StringTokenizer

delim