Top Description Fields Constructors Methods
java.io

public Class StreamTokenizer

extends Object
Class Inheritance
Imports
java.util.Arrays
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:

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.

Author
James Gosling
Since
1.0
See Also
java.io.StreamTokenizer#nextToken(), java.io.StreamTokenizer#TT_EOF

Field Summary

Modifier and TypeField and Description
private char[]
buf

private static final byte
CT_ALPHA

private static final byte
CT_COMMENT

private static final byte
CT_DIGIT

private static final byte
CT_QUOTE

private static final byte
CT_WHITESPACE

private final byte[]
ctype

private boolean
eolIsSignificantP

private boolean
forceLower

private InputStream
input

private int
LINENO

The line number of the last token read

private static final int
NEED_CHAR

public double
nval

If the current token is a number, this field contains the value of that number.

private int
peekc

The next character to be considered by the nextToken method.

private boolean
pushedBack

private Reader
reader

private static final int
SKIP_LF

private boolean
slashSlashCommentsP

private boolean
slashStarCommentsP

public String
sval

If the current token is a word token, this field contains a string giving the characters of the word token.

public static final int
TT_EOF

A constant indicating that the end of the stream has been read.

public static final int
TT_EOL

A constant indicating that the end of the line has been read.

private static final int
TT_NOTHING

public static final int
TT_NUMBER

A constant indicating that a number token has been read.

public static final int
TT_WORD

A constant indicating that a word token has been read.

public int
ttype

After a call to the nextToken method, this field contains the type of the token just read.

Constructor Summary

AccessConstructor and Description
private
StreamTokenizer()

Private constructor that initializes everything except the streams.

public
StreamTokenizer(InputStream
an input stream.
is)
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); 
Reader r = new BufferedReader(new InputStreamReader(is));
StreamTokenizer st = new StreamTokenizer(r);

Creates a stream tokenizer that parses the specified input stream.

public
StreamTokenizer(Reader
a Reader object providing the input stream.
r)

Create a tokenizer that parses the given character stream.

Method Summary

Modifier and TypeMethod and Description
public void
commentChar(int
the character.
ch)

Specifies that the character argument starts a single-line comment.

public void
eolIsSignificant(boolean
true indicates that end-of-line characters are separate tokens; false indicates that end-of-line characters are white space.
flag)

Determines whether or not ends of line are treated as tokens.

public int

Returns:

the current line number of this stream tokenizer.
lineno()

Returns the current line number.

public void
lowerCaseMode(boolean
true indicates that all word tokens should be lowercased.
fl)

Determines whether or not word token are automatically lowercased.

public int

Returns:

the value of the ttype field.
nextToken()

Parses the next token from the input stream of this tokenizer.

public void
ordinaryChar(int
the character.
ch)

Specifies that the character argument is "ordinary" in this tokenizer.

public void
ordinaryChars(int
the low end of the range.
low, int
the high end of the range.
hi)

Specifies that all characters c in the range low <= c <= high are "ordinary" in this tokenizer.

public void
parseNumbers()

Specifies that numbers should be parsed by this tokenizer.

public void
pushBack()

Causes the next call to the nextToken method of this tokenizer to return the current value in the ttype field, and not to modify the value in the nval or sval field.

public void
quoteChar(int
the character.
ch)

Specifies that matching pairs of this character delimit string constants in this tokenizer.

private int
read()

Read the next character

public void
resetSyntax()

Resets this tokenizer's syntax table so that all characters are "ordinary." See the ordinaryChar method for more information on a character being ordinary.

public void
slashSlashComments(boolean
true indicates to recognize and ignore C++-style comments.
flag)

Determines whether or not the tokenizer recognizes C++-style comments.

public void
slashStarComments(boolean
true indicates to recognize and ignore C-style comments.
flag)

Determines whether or not the tokenizer recognizes C-style comments.

public String

Returns:

a string representation of the token
toString()

Overrides java.lang.Object.toString.

Returns the string representation of the current stream token and the line number it occurs on.

public void
whitespaceChars(int
the low end of the range.
low, int
the high end of the range.
hi)

Specifies that all characters c in the range low <= c <= high are white space characters.

public void
wordChars(int
the low end of the range.
low, int
the high end of the range.
hi)

Specifies that all characters c in the range low <= c <= high are word constituents.

Inherited from java.lang.Object:
cloneequalsfinalizegetClasshashCodenotifynotifyAllwaitwaitwait

Field Detail

bufback to summary
private char[] buf
CT_ALPHAback to summary
private static final byte CT_ALPHA
CT_COMMENTback to summary
private static final byte CT_COMMENT
CT_DIGITback to summary
private static final byte CT_DIGIT
CT_QUOTEback to summary
private static final byte CT_QUOTE
CT_WHITESPACEback to summary
private static final byte CT_WHITESPACE
ctypeback to summary
private final byte[] ctype
eolIsSignificantPback to summary
private boolean eolIsSignificantP
forceLowerback to summary
private boolean forceLower
inputback to summary
private InputStream input
LINENOback to summary
private int LINENO

The line number of the last token read

NEED_CHARback to summary
private static final int NEED_CHAR
nvalback to summary
public double nval

If the current token is a number, this field contains the value of that number. The current token is a number when the value of the ttype field is TT_NUMBER.

The initial value of this field is 0.0.

See Also
java.io.StreamTokenizer#TT_NUMBER, java.io.StreamTokenizer#ttype
peekcback to summary
private int peekc

The next character to be considered by the nextToken method. May also be NEED_CHAR to indicate that a new character should be read, or SKIP_LF to indicate that a new character should be read and, if it is a '\n' character, it should be discarded and a second new character should be read.

pushedBackback to summary
private boolean pushedBack
readerback to summary
private Reader reader
SKIP_LFback to summary
private static final int SKIP_LF
slashSlashCommentsPback to summary
private boolean slashSlashCommentsP
slashStarCommentsPback to summary
private boolean slashStarCommentsP
svalback to summary
public String 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 ttype field is TT_WORD. The current token is a quoted string token when the value of the ttype field is a quote character.

The initial value of this field is null.

See Also
java.io.StreamTokenizer#quoteChar(int), java.io.StreamTokenizer#TT_WORD, java.io.StreamTokenizer#ttype
TT_EOFback to summary
public static final int TT_EOF

A constant indicating that the end of the stream has been read.

TT_EOLback to summary
public static final int TT_EOL

A constant indicating that the end of the line has been read.

TT_NOTHINGback to summary
private static final int TT_NOTHING
TT_NUMBERback to summary
public static final int TT_NUMBER

A constant indicating that a number token has been read.

TT_WORDback to summary
public static final int TT_WORD

A constant indicating that a word token has been read.

ttypeback to summary
public int ttype

After a call to the nextToken method, 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_WORD indicates that the token is a word.
  • TT_NUMBER indicates that the token is a number.
  • TT_EOL indicates that the end of line has been read. The field can only have this value if the eolIsSignificant method has been called with the argument true.
  • TT_EOF indicates that the end of the input stream has been reached.

The initial value of this field is -4.

See Also
java.io.StreamTokenizer#eolIsSignificant(boolean), java.io.StreamTokenizer#nextToken(), java.io.StreamTokenizer#quoteChar(int), java.io.StreamTokenizer#TT_EOF, java.io.StreamTokenizer#TT_EOL, java.io.StreamTokenizer#TT_NUMBER, java.io.StreamTokenizer#TT_WORD

Constructor Detail

StreamTokenizerback to summary
private StreamTokenizer()

Private constructor that initializes everything except the streams.

StreamTokenizerback to summary
public StreamTokenizer(InputStream is)

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); 
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:InputStream

an input stream.

Annotations
@Deprecated
@SuppressWarnings:this-escape
See Also
java.io.BufferedReader, java.io.InputStreamReader, java.io.StreamTokenizer#StreamTokenizer(java.io.Reader)
StreamTokenizerback to summary
public StreamTokenizer(Reader r)

Create a tokenizer that parses the given character stream.

Parameters
r:Reader

a Reader object providing the input stream.

Annotations
@SuppressWarnings:this-escape
Since
1.1

Method Detail

commentCharback to summary
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:int

the character.

eolIsSignificantback to summary
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; the nextToken method returns TT_EOL and also sets the ttype field 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 flag is false, end-of-line characters are treated as white space and serve only to separate tokens.

Parameters
flag:boolean

true indicates that end-of-line characters are separate tokens; false indicates that end-of-line characters are white space.

See Also
java.io.StreamTokenizer#nextToken(), java.io.StreamTokenizer#ttype, java.io.StreamTokenizer#TT_EOL
linenoback to summary
public int lineno()

Returns the current line number.

Returns:int

the current line number of this stream tokenizer.

lowerCaseModeback to summary
public void lowerCaseMode(boolean fl)

Determines whether or not word token are automatically lowercased. If the flag argument is true, then the value in the sval field is lowercased whenever a word token is returned (the ttype field has the value TT_WORD) by the nextToken method of this tokenizer.

If the flag argument is false, then the sval field is not modified.

Parameters
fl:boolean

true indicates that all word tokens should be lowercased.

See Also
java.io.StreamTokenizer#nextToken(), java.io.StreamTokenizer#ttype, java.io.StreamTokenizer#TT_WORD
nextTokenback to summary
public int nextToken() throws IOException

Parses the next token from the input stream of this tokenizer. The type of the next token is returned in the ttype field. Additional information about the token may be in the nval field or the sval field 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:int

the value of the ttype field.

Exceptions
IOException:
if an I/O error occurs.
See Also
java.io.StreamTokenizer#nval, java.io.StreamTokenizer#sval, java.io.StreamTokenizer#ttype
ordinaryCharback to summary
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 sets ttype field to the character value.

Making a line terminator character "ordinary" may interfere with the ability of a StreamTokenizer to count lines. The lineno method may no longer reflect the presence of such terminator characters in its line count.

Parameters
ch:int

the character.

See Also
java.io.StreamTokenizer#ttype
ordinaryCharsback to summary
public void ordinaryChars(int low, int hi)

Specifies that all characters c in the range low <= c <= high are "ordinary" in this tokenizer. See the ordinaryChar method for more information on a character being ordinary.

Parameters
low:int

the low end of the range.

hi:int

the high end of the range.

See Also
java.io.StreamTokenizer#ordinaryChar(int)
parseNumbersback to summary
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 ttype field to the value TT_NUMBER and putting the numeric value of the token into the nval field.

See Also
java.io.StreamTokenizer#nval, java.io.StreamTokenizer#TT_NUMBER, java.io.StreamTokenizer#ttype
pushBackback to summary
public void pushBack()

Causes the next call to the nextToken method of this tokenizer to return the current value in the ttype field, and not to modify the value in the nval or sval field.

See Also
java.io.StreamTokenizer#nextToken(), java.io.StreamTokenizer#nval, java.io.StreamTokenizer#sval, java.io.StreamTokenizer#ttype
quoteCharback to summary
public void quoteChar(int ch)

Specifies that matching pairs of this character delimit string constants in this tokenizer.

When the nextToken method encounters a string constant, the ttype field is set to the string delimiter and the sval field 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:int

the character.

See Also
java.io.StreamTokenizer#nextToken(), java.io.StreamTokenizer#sval, java.io.StreamTokenizer#ttype
readback to summary
private int read() throws IOException

Read the next character

resetSyntaxback to summary
public void resetSyntax()

Resets this tokenizer's syntax table so that all characters are "ordinary." See the ordinaryChar method for more information on a character being ordinary.

See Also
java.io.StreamTokenizer#ordinaryChar(int)
slashSlashCommentsback to summary
public void slashSlashComments(boolean flag)

Determines whether or not the tokenizer recognizes C++-style comments. If the flag argument is true, 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:boolean

true indicates to recognize and ignore C++-style comments.

slashStarCommentsback to summary
public void slashStarComments(boolean flag)

Determines whether or not the tokenizer recognizes C-style comments. If the flag argument is true, 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:boolean

true indicates to recognize and ignore C-style comments.

toStringback to summary
public String toString()

Overrides java.lang.Object.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
Returns:String

a string representation of the token

See Also
java.io.StreamTokenizer#nval, java.io.StreamTokenizer#sval, java.io.StreamTokenizer#ttype
whitespaceCharsback to summary
public void whitespaceChars(int low, int hi)

Specifies that all characters c in the range low <= c <= high are 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:int

the low end of the range.

hi:int

the high end of the range.

wordCharsback to summary
public void wordChars(int low, int hi)

Specifies that all characters c in the range low <= c <= high are word constituents. A word token consists of a word constituent followed by zero or more word constituents or number constituents.

Parameters
low:int

the low end of the range.

hi:int

the high end of the range.