OpenJDK 1.23 · java.util.StringTokenizer · APIdia, the JavaDoc alternative

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 (String r : result)
        System.out.println(r);

prints the following output:

    this
    is
    a
    test

Field Summary

Modifier and Type	Field and Description
private int	currentPosition
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.
private String	delimiters
private boolean	delimsChanged
private boolean	hasSurrogates If delimiters include any surrogates (including surrogate pairs), hasSurrogates is true and the tokenizer uses the different code path.
private int	maxDelimCodePoint maxDelimCodePoint stores the value of the delimiter character with the highest value.
private int	maxPosition
private int	newPosition
private boolean	retDelims
private String	str

Constructor Summary

Access	Constructor and Description
public	StringTokenizer(String a string to be parsed. str, String the delimiters. delim, boolean flag indicating whether to return the delimiters as tokens. returnDelims) Constructs a string tokenizer for the specified string.
public	StringTokenizer(String a string to be parsed. str, String the delimiters. delim) Constructs a string tokenizer for the specified string.
public	StringTokenizer(String a string to be parsed. str) Constructs a string tokenizer for the specified string.

Method Summary

Modifier and Type	Method and Description
public int	Returns: the number of tokens remaining in the string using the current delimiter set. countTokens() Calculates the number of times that this tokenizer's `nextToken` method can be called before it generates an exception.
public boolean	Returns: `true` if there are more tokens; `false` otherwise. hasMoreElements() Implements java.util.Enumeration.hasMoreElements. Returns the same value as the `hasMoreTokens` method.
public boolean	Returns: `true` if and only if there is at least one token in the string after the current position; `false` otherwise. hasMoreTokens() Tests if there are more tokens available from this tokenizer's string.
private boolean	isDelimiter(int codePoint)
public Object	Returns: the next token in the string. nextElement() Implements java.util.Enumeration.nextElement. Returns the same value as the `nextToken` method, except that its declared return value is `Object` rather than `String`.
public String	Returns: the next token from this string tokenizer. nextToken() Returns the next token from this string tokenizer.
public String	Returns: the next token, after switching to the new delimiter set. nextToken(String the new delimiters. delim) Returns the next token in this string tokenizer's string.
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.
private void	setMaxDelimCodePoint() Set maxDelimCodePoint to the highest char in the delimiter set.
private int	skipDelimiters(int startPos) Skips delimiters starting from the specified position.

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

Field Detail

currentPosition	back to summary
private int currentPosition

delimiterCodePoints	back to summary
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	back to summary
private String delimiters

delimsChanged	back to summary
private boolean delimsChanged

hasSurrogates	back to summary
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	back to summary
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	back to summary
private int maxPosition

newPosition	back to summary
private int newPosition

retDelims	back to summary
private boolean retDelims

str	back to summary
private String str

Constructor Detail

StringTokenizer back to summary

StringTokenizer	back to summary
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 consisting of a single Unicode code point of the delimiter (which may be one or two `char`s). 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:String a string to be parsed. delim:String the delimiters. returnDelims:boolean flag indicating whether to return the delimiters as tokens. Exceptions NullPointerException: if str is `null`

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 consisting of a single Unicode code point of the delimiter (which may be one or two chars). 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:String: a string to be parsed.
delim:String: the delimiters.
returnDelims:boolean: flag indicating whether to return the delimiters as tokens.

Exceptions

NullPointerException:: if str is null

StringTokenizer back to summary

StringTokenizer	back to summary
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 str:String a string to be parsed. delim:String the delimiters. Exceptions NullPointerException: if str is `null`

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

str:String: a string to be parsed.
delim:String: the delimiters.

Exceptions

NullPointerException:: if str is null

StringTokenizer back to summary

StringTokenizer	back to summary
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 str:String a string to be parsed. Exceptions NullPointerException: if str is `null`

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

str:String: a string to be parsed.

Exceptions

NullPointerException:: if str is null

Method Detail

countTokens back to summary

countTokens	back to summary
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. Returns:int the number of tokens remaining in the string using the current delimiter set. See Also `java.util.StringTokenizer#nextToken()`

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.

Returns:int: the number of tokens remaining in the string using the current delimiter set.
See Also: java.util.StringTokenizer#nextToken()

hasMoreElements back to summary

hasMoreElements	back to summary
public boolean hasMoreElements() Implements java.util.Enumeration.hasMoreElements. Returns the same value as the `hasMoreTokens` method. It exists so that this class can implement the `Enumeration` interface. Returns:boolean `true` if there are more tokens; `false` otherwise. See Also `java.util.Enumeration`, `java.util.StringTokenizer#hasMoreTokens()`

public boolean hasMoreElements()

Implements java.util.Enumeration.hasMoreElements.

Returns the same value as the hasMoreTokens method. It exists so that this class can implement the Enumeration interface.

Returns:boolean: true if there are more tokens; false otherwise.
See Also: java.util.Enumeration, java.util.StringTokenizer#hasMoreTokens()

hasMoreTokens back to summary

hasMoreTokens	back to summary
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. Returns:boolean `true` if and only if there is at least one token in the string after the current position; `false` otherwise.

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.

Returns:boolean: true if and only if there is at least one token in the string after the current position; false otherwise.

isDelimiter	back to summary
private boolean isDelimiter(int codePoint)

nextElement back to summary

nextElement	back to summary
public Object nextElement() Implements java.util.Enumeration.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. Returns:Object the next token in the string. Exceptions NoSuchElementException: if there are no more tokens in this tokenizer's string. See Also `java.util.Enumeration`, `java.util.StringTokenizer#nextToken()`

public Object nextElement()

Implements java.util.Enumeration.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.

Returns:Object

the next token in the string.

Exceptions

NoSuchElementException:: if there are no more tokens in this tokenizer's string.

nextToken	back to summary
public String nextToken() Returns the next token from this string tokenizer. Returns:String the next token from this string tokenizer. Exceptions NoSuchElementException: if there are no more tokens in this tokenizer's string.

nextToken

back to summary

public String nextToken()

Returns the next token from this string tokenizer.

Returns:String

the next token from this string tokenizer.

Exceptions

NoSuchElementException:: if there are no more tokens in this tokenizer's string.

nextToken back to summary

nextToken	back to summary
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 delim:String the new delimiters. Returns:String the next token, after switching to the new delimiter set. Exceptions NoSuchElementException: if there are no more tokens in this tokenizer's string. NullPointerException: if delim is `null`

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

delim:String: the new delimiters.

Returns:String

the next token, after switching to the new delimiter set.

Exceptions

NoSuchElementException:: if there are no more tokens in this tokenizer's string.
NullPointerException:: if delim is null

scanToken	back to summary
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.

setMaxDelimCodePoint	back to summary
private void setMaxDelimCodePoint() Set maxDelimCodePoint to the highest char in the delimiter set.

skipDelimiters	back to summary
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.

public Class StringTokenizer

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