Class StreamTokenizer
StreamTokenizer class takes an input stream and
parses it into "tokens", allowing the tokens to be
read one at a time. The parsing process is controlled by a table
and a number of flags that can be set to various states. The
stream tokenizer can recognize identifiers, numbers, quoted
strings, and various comment styles.
Each byte read from the input stream is regarded as a character
in the range '\u0000' through '\u00FF'.
The character value is used to look up five possible attributes of
the character: white space, alphabetic,
numeric, string quote, and comment character.
Each character can have zero or more of these attributes.
In addition, an instance has four flags. These flags indicate:
- Whether line terminators are to be returned as tokens or treated as white space that merely separates tokens.
- Whether C-style comments are to be recognized and skipped.
- Whether C++-style comments are to be recognized and skipped.
- Whether the characters of identifiers are converted to lowercase.
A typical application first constructs an instance of this class,
sets up the syntax tables, and then repeatedly loops calling the
nextToken method in each iteration of the loop until
it returns the value TT_EOF.
- Since:
- 1.0
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Field Summary
FieldsModifier and TypeFieldDescriptiondoubleIf the current token is a number, this field contains the value of that number.If the current token is a word token, this field contains a string giving the characters of the word token.static final intA constant indicating that the end of the stream has been read.static final intA constant indicating that the end of the line has been read.static final intA constant indicating that a number token has been read.static final intA constant indicating that a word token has been read.intAfter a call to thenextTokenmethod, this field contains the type of the token just read. -
Constructor Summary
ConstructorsConstructorDescriptionDeprecated.As of JDK version 1.1, the preferred way to tokenize an input stream is to convert it into a character stream, for example:Create a tokenizer that parses the given character stream. -
Method Summary
Modifier and TypeMethodDescriptionvoidcommentChar(int ch) Specifies that the character argument starts a single-line comment.voideolIsSignificant(boolean flag) Determines whether or not ends of line are treated as tokens.intlineno()Returns the current line number.voidlowerCaseMode(boolean fl) Determines whether or not word token are automatically lowercased.intParses the next token from the input stream of this tokenizer.voidordinaryChar(int ch) Specifies that the character argument is "ordinary" in this tokenizer.voidordinaryChars(int low, int hi) Specifies that all characters c in the rangelow <= c <= highare "ordinary" in this tokenizer.voidSpecifies that numbers should be parsed by this tokenizer.voidpushBack()Causes the next call to thenextTokenmethod of this tokenizer to return the current value in thettypefield, and not to modify the value in thenvalorsvalfield.voidquoteChar(int ch) Specifies that matching pairs of this character delimit string constants in this tokenizer.voidResets this tokenizer's syntax table so that all characters are "ordinary."voidslashSlashComments(boolean flag) Determines whether or not the tokenizer recognizes C++-style comments.voidslashStarComments(boolean flag) Determines whether or not the tokenizer recognizes C-style comments.toString()Returns the string representation of the current stream token and the line number it occurs on.voidwhitespaceChars(int low, int hi) Specifies that all characters c in the rangelow <= c <= highare white space characters.voidwordChars(int low, int hi) Specifies that all characters c in the rangelow <= c <= highare word constituents.
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Field Details
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ttype
public int ttypeAfter a call to thenextTokenmethod, this field contains the type of the token just read. For a single character token, its value is the single character, converted to an integer. For a quoted string token, its value is the quote character. Otherwise, its value is one of the following:TT_WORDindicates that the token is a word.TT_NUMBERindicates that the token is a number.TT_EOLindicates that the end of line has been read. The field can only have this value if theeolIsSignificantmethod has been called with the argumenttrue.TT_EOFindicates that the end of the input stream has been reached.
The initial value of this field is -4.
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TT_EOF
public static final int TT_EOFA constant indicating that the end of the stream has been read.- See Also:
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TT_EOL
public static final int TT_EOLA constant indicating that the end of the line has been read.- See Also:
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TT_NUMBER
public static final int TT_NUMBERA constant indicating that a number token has been read.- See Also:
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TT_WORD
public static final int TT_WORDA constant indicating that a word token has been read.- See Also:
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sval
If the current token is a word token, this field contains a string giving the characters of the word token. When the current token is a quoted string token, this field contains the body of the string.The current token is a word when the value of the
ttypefield isTT_WORD. The current token is a quoted string token when the value of thettypefield is a quote character.The initial value of this field is null.
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nval
public double nvalIf the current token is a number, this field contains the value of that number. The current token is a number when the value of thettypefield isTT_NUMBER.The initial value of this field is 0.0.
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Constructor Details
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StreamTokenizer
Deprecated.As of JDK version 1.1, the preferred way to tokenize an input stream is to convert it into a character stream, for example:Reader r = new BufferedReader(new InputStreamReader(is)); StreamTokenizer st = new StreamTokenizer(r);Creates a stream tokenizer that parses the specified input stream. The stream tokenizer is initialized to the following default state:- All byte values
'A'through'Z','a'through'z', and'\u00A0'through'\u00FF'are considered to be alphabetic. - All byte values
'\u0000'through'\u0020'are considered to be white space. '/'is a comment character.- Single quote
'\''and double quote'"'are string quote characters. - Numbers are parsed.
- Ends of lines are treated as white space, not as separate tokens.
- C-style and C++-style comments are not recognized.
- Parameters:
is- an input stream.- See Also:
- All byte values
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StreamTokenizer
Create a tokenizer that parses the given character stream.- Parameters:
r- a Reader object providing the input stream.- Since:
- 1.1
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Method Details
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resetSyntax
public void resetSyntax()Resets this tokenizer's syntax table so that all characters are "ordinary." See theordinaryCharmethod for more information on a character being ordinary.- See Also:
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wordChars
public void wordChars(int low, int hi) Specifies that all characters c in the rangelow <= c <= highare word constituents. A word token consists of a word constituent followed by zero or more word constituents or number constituents.- Parameters:
low- the low end of the range.hi- the high end of the range.
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whitespaceChars
public void whitespaceChars(int low, int hi) Specifies that all characters c in the rangelow <= c <= highare white space characters. White space characters serve only to separate tokens in the input stream.Any other attribute settings for the characters in the specified range are cleared.
- Parameters:
low- the low end of the range.hi- the high end of the range.
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ordinaryChars
public void ordinaryChars(int low, int hi) Specifies that all characters c in the rangelow <= c <= highare "ordinary" in this tokenizer. See theordinaryCharmethod for more information on a character being ordinary.- Parameters:
low- the low end of the range.hi- the high end of the range.- See Also:
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ordinaryChar
public void ordinaryChar(int ch) Specifies that the character argument is "ordinary" in this tokenizer. It removes any special significance the character has as a comment character, word component, string delimiter, white space, or number character. When such a character is encountered by the parser, the parser treats it as a single-character token and setsttypefield to the character value.Making a line terminator character "ordinary" may interfere with the ability of a
StreamTokenizerto count lines. Thelinenomethod may no longer reflect the presence of such terminator characters in its line count.- Parameters:
ch- the character.- See Also:
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commentChar
public void commentChar(int ch) Specifies that the character argument starts a single-line comment. All characters from the comment character to the end of the line are ignored by this stream tokenizer.Any other attribute settings for the specified character are cleared.
- Parameters:
ch- the character.
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quoteChar
public void quoteChar(int ch) Specifies that matching pairs of this character delimit string constants in this tokenizer.When the
nextTokenmethod encounters a string constant, thettypefield is set to the string delimiter and thesvalfield is set to the body of the string.If a string quote character is encountered, then a string is recognized, consisting of all characters after (but not including) the string quote character, up to (but not including) the next occurrence of that same string quote character, or a line terminator, or end of file. The usual escape sequences such as
"\n"and"\t"are recognized and converted to single characters as the string is parsed.Any other attribute settings for the specified character are cleared.
- Parameters:
ch- the character.- See Also:
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parseNumbers
public void parseNumbers()Specifies that numbers should be parsed by this tokenizer. The syntax table of this tokenizer is modified so that each of the twelve characters:0 1 2 3 4 5 6 7 8 9 . -has the "numeric" attribute.
When the parser encounters a word token that has the format of a double precision floating-point number, it treats the token as a number rather than a word, by setting the
ttypefield to the valueTT_NUMBERand putting the numeric value of the token into thenvalfield.- See Also:
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eolIsSignificant
public void eolIsSignificant(boolean flag) Determines whether or not ends of line are treated as tokens. If the flag argument is true, this tokenizer treats end of lines as tokens; thenextTokenmethod returnsTT_EOLand also sets thettypefield to this value when an end of line is read.A line is a sequence of characters ending with either a carriage-return character (
'\r') or a newline character ('\n'). In addition, a carriage-return character followed immediately by a newline character is treated as a single end-of-line token.If the
flagis false, end-of-line characters are treated as white space and serve only to separate tokens.- Parameters:
flag-trueindicates that end-of-line characters are separate tokens;falseindicates that end-of-line characters are white space.- See Also:
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slashStarComments
public void slashStarComments(boolean flag) Determines whether or not the tokenizer recognizes C-style comments. If the flag argument istrue, this stream tokenizer recognizes C-style comments. All text between successive occurrences of/*and*/are discarded.If the flag argument is
false, then C-style comments are not treated specially.- Parameters:
flag-trueindicates to recognize and ignore C-style comments.
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slashSlashComments
public void slashSlashComments(boolean flag) Determines whether or not the tokenizer recognizes C++-style comments. If the flag argument istrue, this stream tokenizer recognizes C++-style comments. Any occurrence of two consecutive slash characters ('/') is treated as the beginning of a comment that extends to the end of the line.If the flag argument is
false, then C++-style comments are not treated specially.- Parameters:
flag-trueindicates to recognize and ignore C++-style comments.
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lowerCaseMode
public void lowerCaseMode(boolean fl) Determines whether or not word token are automatically lowercased. If the flag argument istrue, then the value in thesvalfield is lowercased whenever a word token is returned (thettypefield has the valueTT_WORD) by thenextTokenmethod of this tokenizer.If the flag argument is
false, then thesvalfield is not modified.- Parameters:
fl-trueindicates that all word tokens should be lowercased.- See Also:
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nextToken
Parses the next token from the input stream of this tokenizer. The type of the next token is returned in thettypefield. Additional information about the token may be in thenvalfield or thesvalfield of this tokenizer.Typical clients of this class first set up the syntax tables and then sit in a loop calling nextToken to parse successive tokens until TT_EOF is returned.
- Returns:
- the value of the
ttypefield. - Throws:
IOException- if an I/O error occurs.- See Also:
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pushBack
public void pushBack()Causes the next call to thenextTokenmethod of this tokenizer to return the current value in thettypefield, and not to modify the value in thenvalorsvalfield.- See Also:
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lineno
public int lineno()Returns the current line number.- Returns:
- the current line number of this stream tokenizer.
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toString
Returns the string representation of the current stream token and the line number it occurs on.The precise string returned is unspecified, although the following example can be considered typical:
Token['a'], line 10
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