Class: java.io.StreamTokenizer
- public class StreamTokenizer
The
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.
Methods
-
StreamTokenizertop
public StreamTokenizer(InputStream is)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.
- All byte values
-
StreamTokenizertop
public StreamTokenizer(Reader r)Create a tokenizer that parses the given character stream. -
commentChartop
public void commentChar(int ch)Specified 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.
-
eolIsSignificanttop
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. -
linenotop
public int lineno()Return the current line number. -
lowerCaseModetop
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_WORDby thenextTokenmethod of this tokenizer.If the flag argument is
false, then thesvalfield is not modified. -
nextTokentop
public int nextToken() throws IOExceptionParses 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.
-
ordinaryChartop
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. -
ordinaryCharstop
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. -
parseNumberstop
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. -
pushBacktop
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. -
quoteChartop
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.
-
resetSyntaxtop
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. -
slashSlashCommentstop
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. -
slashStarCommentstop
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. -
toStringtop
public String 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
-
whitespaceCharstop
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.
-
wordCharstop
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.
Fields
-
TT_EOF
public static final int TT_EOF = -1A constant indicating that the end of the stream has been read. -
TT_EOL
public static final int TT_EOL = 10A constant indicating that the end of the line has been read. -
TT_NUMBER
public static final int TT_NUMBER = -2A constant indicating that a number token has been read. -
TT_WORD
public static final int TT_WORD = -3A constant indicating that a word token has been read. -
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.
-
sval
public String svalIf 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.
-
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.