java/15 : java.base/java/io/StreamTokenizer.java

StreamTokenizer
https://openjdk.java.net/
GPLv2 + Classpath Exception
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package java.io;

import 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 '\u005Cu0000' through '\u005Cu00FF'. 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. 
Author:  James Gosling
See Also: nextToken()
TT_EOF
Since:   1.0/**
 * The {@code 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.
 * <p>
 * Each byte read from the input stream is regarded as a character
 * in the range {@code '\u005Cu0000'} through {@code '\u005Cu00FF'}.
 * The character value is used to look up five possible attributes of
 * the character: <i>white space</i>, <i>alphabetic</i>,
 * <i>numeric</i>, <i>string quote</i>, and <i>comment character</i>.
 * Each character can have zero or more of these attributes.
 * <p>
 * In addition, an instance has four flags. These flags indicate:
 * <ul>
 * <li>Whether line terminators are to be returned as tokens or treated
 *     as white space that merely separates tokens.
 * <li>Whether C-style comments are to be recognized and skipped.
 * <li>Whether C++-style comments are to be recognized and skipped.
 * <li>Whether the characters of identifiers are converted to lowercase.
 * </ul>
 * <p>
 * A typical application first constructs an instance of this class,
 * sets up the syntax tables, and then repeatedly loops calling the
 * {@code nextToken} method in each iteration of the loop until
 * it returns the value {@code TT_EOF}.
 *
 * @author  James Gosling
 * @see     java.io.StreamTokenizer#nextToken()
 * @see     java.io.StreamTokenizer#TT_EOF
 * @since   1.0
 */

public class StreamTokenizer {

    /* Only one of these will be non-null */
    private Reader reader = null;
    private InputStream input = null;

    private char buf[] = new char[20];

    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.
/**
     * 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.
     */
    private int peekc = NEED_CHAR;

    private static final int NEED_CHAR = Integer.MAX_VALUE;
    private static final int SKIP_LF = Integer.MAX_VALUE - 1;

    private boolean pushedBack;
    private boolean forceLower;
    The line number of the last token read /** The line number of the last token read */
    private int LINENO = 1;

    private boolean eolIsSignificantP = false;
    private boolean slashSlashCommentsP = false;
    private boolean slashStarCommentsP = false;

    private byte ctype[] = new byte[256];
    private static final byte CT_WHITESPACE = 1;
    private static final byte CT_DIGIT = 2;
    private static final byte CT_ALPHA = 4;
    private static final byte CT_QUOTE = 8;
    private static final byte CT_COMMENT = 16;

    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: eolIsSignificant(boolean)
nextToken()
quoteChar(int)
TT_EOF
TT_EOL
TT_NUMBER
TT_WORD/**
     * After a call to the {@code 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:
     * <ul>
     * <li>{@code TT_WORD} indicates that the token is a word.
     * <li>{@code TT_NUMBER} indicates that the token is a number.
     * <li>{@code TT_EOL} indicates that the end of line has been read.
     *     The field can only have this value if the
     *     {@code eolIsSignificant} method has been called with the
     *     argument {@code true}.
     * <li>{@code TT_EOF} indicates that the end of the input stream
     *     has been reached.
     * </ul>
     * <p>
     * The initial value of this field is -4.
     *
     * @see     java.io.StreamTokenizer#eolIsSignificant(boolean)
     * @see     java.io.StreamTokenizer#nextToken()
     * @see     java.io.StreamTokenizer#quoteChar(int)
     * @see     java.io.StreamTokenizer#TT_EOF
     * @see     java.io.StreamTokenizer#TT_EOL
     * @see     java.io.StreamTokenizer#TT_NUMBER
     * @see     java.io.StreamTokenizer#TT_WORD
     */
    public int ttype = TT_NOTHING;

    A constant indicating that the end of the stream has been read.
/**
     * A constant indicating that the end of the stream has been read.
     */
    public static final int TT_EOF = -1;

    A constant indicating that the end of the line has been read.
/**
     * A constant indicating that the end of the line has been read.
     */
    public static final int TT_EOL = '\n';

    A constant indicating that a number token has been read.
/**
     * A constant indicating that a number token has been read.
     */
    public static final int TT_NUMBER = -2;

    A constant indicating that a word token has been read.
/**
     * A constant indicating that a word token has been read.
     */
    public static final int TT_WORD = -3;

    /* A constant indicating that no token has been read, used for
     * initializing ttype.  FIXME This could be made public and
     * made available as the part of the API in a future release.
     */
    private static final int TT_NOTHING = -4;

    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: quoteChar(int)
TT_WORD
ttype/**
     * 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.
     * <p>
     * The current token is a word when the value of the
     * {@code ttype} field is {@code TT_WORD}. The current token is
     * a quoted string token when the value of the {@code ttype} field is
     * a quote character.
     * <p>
     * The initial value of this field is null.
     *
     * @see     java.io.StreamTokenizer#quoteChar(int)
     * @see     java.io.StreamTokenizer#TT_WORD
     * @see     java.io.StreamTokenizer#ttype
     */
    public String sval;

    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: TT_NUMBER
ttype/**
     * 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 {@code ttype} field is {@code TT_NUMBER}.
     * <p>
     * The initial value of this field is 0.0.
     *
     * @see     java.io.StreamTokenizer#TT_NUMBER
     * @see     java.io.StreamTokenizer#ttype
     */
    public double nval;

    Private constructor that initializes everything except the streams. /** Private constructor that initializes everything except the streams. */
    private StreamTokenizer() {
        wordChars('a', 'z');
        wordChars('A', 'Z');
        wordChars(128 + 32, 255);
        whitespaceChars(0, ' ');
        commentChar('/');
        quoteChar('"');
        quoteChar('\'');
        parseNumbers();
    }

    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 '\u005Cu00A0' through '\u005Cu00FF' are considered to be alphabetic. 
All byte values '\u005Cu0000' through '\u005Cu0020' are considered to be white space. 
'/' is a comment character. 
Single quote '\u005C'' 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.

Params: is –        an input stream.
See Also: BufferedReader
InputStreamReader
StreamTokenizer(Reader)
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:
     * <ul>
     * <li>All byte values {@code 'A'} through {@code 'Z'},
     *     {@code 'a'} through {@code 'z'}, and
     *     {@code '\u005Cu00A0'} through {@code '\u005Cu00FF'} are
     *     considered to be alphabetic.
     * <li>All byte values {@code '\u005Cu0000'} through
     *     {@code '\u005Cu0020'} are considered to be white space.
     * <li>{@code '/'} is a comment character.
     * <li>Single quote {@code '\u005C''} and double quote {@code '"'}
     *     are string quote characters.
     * <li>Numbers are parsed.
     * <li>Ends of lines are treated as white space, not as separate tokens.
     * <li>C-style and C++-style comments are not recognized.
     * </ul>
     *
     * @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:
     * <blockquote><pre>
     *   Reader r = new BufferedReader(new InputStreamReader(is));
     *   StreamTokenizer st = new StreamTokenizer(r);
     * </pre></blockquote>
     *
     * @param      is        an input stream.
     * @see        java.io.BufferedReader
     * @see        java.io.InputStreamReader
     * @see        java.io.StreamTokenizer#StreamTokenizer(java.io.Reader)
     */
    @Deprecated
    public StreamTokenizer(InputStream is) {
        this();
        if (is == null) {
            throw new NullPointerException();
        }
        input = is;
    }

    Create a tokenizer that parses the given character stream.
Params: r –  a Reader object providing the input stream.
Since:   1.1/**
     * Create a tokenizer that parses the given character stream.
     *
     * @param r  a Reader object providing the input stream.
     * @since   1.1
     */
    public StreamTokenizer(Reader r) {
        this();
        if (r == null) {
            throw new NullPointerException();
        }
        reader = r;
    }

    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: ordinaryChar(int)/**
     * Resets this tokenizer's syntax table so that all characters are
     * "ordinary." See the {@code ordinaryChar} method
     * for more information on a character being ordinary.
     *
     * @see     java.io.StreamTokenizer#ordinaryChar(int)
     */
    public void resetSyntax() {
        for (int i = ctype.length; --i >= 0;)
            ctype[i] = 0;
    }

    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.
Params: low –   the low end of the range.
hi –    the high end of the range./**
     * Specifies that all characters <i>c</i> in the range
     * <code>low&nbsp;&lt;=&nbsp;<i>c</i>&nbsp;&lt;=&nbsp;high</code>
     * are word constituents. A word token consists of a word constituent
     * followed by zero or more word constituents or number constituents.
     *
     * @param   low   the low end of the range.
     * @param   hi    the high end of the range.
     */
    public void wordChars(int low, int hi) {
        if (low < 0)
            low = 0;
        if (hi >= ctype.length)
            hi = ctype.length - 1;
        while (low <= hi)
            ctype[low++] |= CT_ALPHA;
    }

    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.
Params: low –   the low end of the range.
hi –    the high end of the range./**
     * Specifies that all characters <i>c</i> in the range
     * <code>low&nbsp;&lt;=&nbsp;<i>c</i>&nbsp;&lt;=&nbsp;high</code>
     * are white space characters. White space characters serve only to
     * separate tokens in the input stream.
     *
     * <p>Any other attribute settings for the characters in the specified
     * range are cleared.
     *
     * @param   low   the low end of the range.
     * @param   hi    the high end of the range.
     */
    public void whitespaceChars(int low, int hi) {
        if (low < 0)
            low = 0;
        if (hi >= ctype.length)
            hi = ctype.length - 1;
        while (low <= hi)
            ctype[low++] = CT_WHITESPACE;
    }

    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. 
Params: low –   the low end of the range.
hi –    the high end of the range.
See Also: ordinaryChar(int)/**
     * Specifies that all characters <i>c</i> in the range
     * <code>low&nbsp;&lt;=&nbsp;<i>c</i>&nbsp;&lt;=&nbsp;high</code>
     * are "ordinary" in this tokenizer. See the
     * {@code ordinaryChar} method for more information on a
     * character being ordinary.
     *
     * @param   low   the low end of the range.
     * @param   hi    the high end of the range.
     * @see     java.io.StreamTokenizer#ordinaryChar(int)
     */
    public void ordinaryChars(int low, int hi) {
        if (low < 0)
            low = 0;
        if (hi >= ctype.length)
            hi = ctype.length - 1;
        while (low <= hi)
            ctype[low++] = 0;
    }

    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. 
Params: ch –   the character.
See Also: ttype/**
     * 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 {@code ttype} field to the
     * character value.
     *
     * <p>Making a line terminator character "ordinary" may interfere
     * with the ability of a {@code StreamTokenizer} to count
     * lines. The {@code lineno} method may no longer reflect
     * the presence of such terminator characters in its line count.
     *
     * @param   ch   the character.
     * @see     java.io.StreamTokenizer#ttype
     */
    public void ordinaryChar(int ch) {
        if (ch >= 0 && ch < ctype.length)
            ctype[ch] = 0;
    }

    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.
Params: ch –   the character./**
     * 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.
     *
     * <p>Any other attribute settings for the specified character are cleared.
     *
     * @param   ch   the character.
     */
    public void commentChar(int ch) {
        if (ch >= 0 && ch < ctype.length)
            ctype[ch] = CT_COMMENT;
    }

    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 "\u005Cn" and "\u005Ct" are recognized and converted to single characters as the string is parsed. 
Any other attribute settings for the specified character are cleared.
Params: ch –   the character.
See Also: nextToken()
sval
ttype/**
     * Specifies that matching pairs of this character delimit string
     * constants in this tokenizer.
     * <p>
     * When the {@code nextToken} method encounters a string
     * constant, the {@code ttype} field is set to the string
     * delimiter and the {@code sval} field is set to the body of
     * the string.
     * <p>
     * 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
     * {@code "\u005Cn"} and {@code "\u005Ct"} are recognized and
     * converted to single characters as the string is parsed.
     *
     * <p>Any other attribute settings for the specified character are cleared.
     *
     * @param   ch   the character.
     * @see     java.io.StreamTokenizer#nextToken()
     * @see     java.io.StreamTokenizer#sval
     * @see     java.io.StreamTokenizer#ttype
     */
    public void quoteChar(int ch) {
        if (ch >= 0 && ch < ctype.length)
            ctype[ch] = CT_QUOTE;
    }

    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: nval
TT_NUMBER
ttype/**
     * Specifies that numbers should be parsed by this tokenizer. The
     * syntax table of this tokenizer is modified so that each of the twelve
     * characters:
     * <blockquote><pre>
     *      0 1 2 3 4 5 6 7 8 9 . -
     * </pre></blockquote>
     * <p>
     * has the "numeric" attribute.
     * <p>
     * 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 {@code ttype}
     * field to the value {@code TT_NUMBER} and putting the numeric
     * value of the token into the {@code nval} field.
     *
     * @see     java.io.StreamTokenizer#nval
     * @see     java.io.StreamTokenizer#TT_NUMBER
     * @see     java.io.StreamTokenizer#ttype
     */
    public void parseNumbers() {
        for (int i = '0'; i <= '9'; i++)
            ctype[i] |= CT_DIGIT;
        ctype['.'] |= CT_DIGIT;
        ctype['-'] |= CT_DIGIT;
    }

    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 ('\u005Cr') or a newline character ('\u005Cn'). 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. 
Params: flag –  true indicates that end-of-line characters are separate tokens; false indicates that end-of-line characters are white space.
See Also: nextToken()
ttype
TT_EOL/**
     * 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 {@code nextToken} method returns
     * {@code TT_EOL} and also sets the {@code ttype} field to
     * this value when an end of line is read.
     * <p>
     * A line is a sequence of characters ending with either a
     * carriage-return character ({@code '\u005Cr'}) or a newline
     * character ({@code '\u005Cn'}). In addition, a carriage-return
     * character followed immediately by a newline character is treated
     * as a single end-of-line token.
     * <p>
     * If the {@code flag} is false, end-of-line characters are
     * treated as white space and serve only to separate tokens.
     *
     * @param   flag   {@code true} indicates that end-of-line characters
     *                 are separate tokens; {@code false} indicates that
     *                 end-of-line characters are white space.
     * @see     java.io.StreamTokenizer#nextToken()
     * @see     java.io.StreamTokenizer#ttype
     * @see     java.io.StreamTokenizer#TT_EOL
     */
    public void eolIsSignificant(boolean flag) {
        eolIsSignificantP = 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. 
Params: flag –  true indicates to recognize and ignore C-style comments./**
     * Determines whether or not the tokenizer recognizes C-style comments.
     * If the flag argument is {@code true}, this stream tokenizer
     * recognizes C-style comments. All text between successive
     * occurrences of {@code /*} and <code>*&#47;</code> are discarded.
     * <p>
     * If the flag argument is {@code false}, then C-style comments
     * are not treated specially.
     *
     * @param   flag   {@code true} indicates to recognize and ignore
     *                 C-style comments.
     */
    public void slashStarComments(boolean flag) {
        slashStarCommentsP = 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. 
Params: flag –  true indicates to recognize and ignore C++-style comments./**
     * Determines whether or not the tokenizer recognizes C++-style comments.
     * If the flag argument is {@code true}, this stream tokenizer
     * recognizes C++-style comments. Any occurrence of two consecutive
     * slash characters ({@code '/'}) is treated as the beginning of
     * a comment that extends to the end of the line.
     * <p>
     * If the flag argument is {@code false}, then C++-style
     * comments are not treated specially.
     *
     * @param   flag   {@code true} indicates to recognize and ignore
     *                 C++-style comments.
     */
    public void slashSlashComments(boolean flag) {
        slashSlashCommentsP = flag;
    }

    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. 
Params: fl –  true indicates that all word tokens should be lowercased.
See Also: nextToken()
ttype
TT_WORD/**
     * Determines whether or not word token are automatically lowercased.
     * If the flag argument is {@code true}, then the value in the
     * {@code sval} field is lowercased whenever a word token is
     * returned (the {@code ttype} field has the
     * value {@code TT_WORD} by the {@code nextToken} method
     * of this tokenizer.
     * <p>
     * If the flag argument is {@code false}, then the
     * {@code sval} field is not modified.
     *
     * @param   fl   {@code true} indicates that all word tokens should
     *               be lowercased.
     * @see     java.io.StreamTokenizer#nextToken()
     * @see     java.io.StreamTokenizer#ttype
     * @see     java.io.StreamTokenizer#TT_WORD
     */
    public void lowerCaseMode(boolean fl) {
        forceLower = fl;
    }

    Read the next character /** Read the next character */
    private int read() throws IOException {
        if (reader != null)
            return reader.read();
        else if (input != null)
            return input.read();
        else
            throw new IllegalStateException();
    }

    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.
Throws: IOException –  if an I/O error occurs.
See Also: nval
sval
ttype
Returns:  the value of the ttype field./**
     * Parses the next token from the input stream of this tokenizer.
     * The type of the next token is returned in the {@code ttype}
     * field. Additional information about the token may be in the
     * {@code nval} field or the {@code sval} field of this
     * tokenizer.
     * <p>
     * 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.
     *
     * @return     the value of the {@code ttype} field.
     * @throws     IOException  if an I/O error occurs.
     * @see        java.io.StreamTokenizer#nval
     * @see        java.io.StreamTokenizer#sval
     * @see        java.io.StreamTokenizer#ttype
     */
    public int nextToken() throws IOException {
        if (pushedBack) {
            pushedBack = false;
            return ttype;
        }
        byte ct[] = ctype;
        sval = null;

        int c = peekc;
        if (c < 0)
            c = NEED_CHAR;
        if (c == SKIP_LF) {
            c = read();
            if (c < 0)
                return ttype = TT_EOF;
            if (c == '\n')
                c = NEED_CHAR;
        }
        if (c == NEED_CHAR) {
            c = read();
            if (c < 0)
                return ttype = TT_EOF;
        }
        ttype = c;              /* Just to be safe */

        /* Set peekc so that the next invocation of nextToken will read
         * another character unless peekc is reset in this invocation
         */
        peekc = NEED_CHAR;

        int ctype = c < 256 ? ct[c] : CT_ALPHA;
        while ((ctype & CT_WHITESPACE) != 0) {
            if (c == '\r') {
                LINENO++;
                if (eolIsSignificantP) {
                    peekc = SKIP_LF;
                    return ttype = TT_EOL;
                }
                c = read();
                if (c == '\n')
                    c = read();
            } else {
                if (c == '\n') {
                    LINENO++;
                    if (eolIsSignificantP) {
                        return ttype = TT_EOL;
                    }
                }
                c = read();
            }
            if (c < 0)
                return ttype = TT_EOF;
            ctype = c < 256 ? ct[c] : CT_ALPHA;
        }

        if ((ctype & CT_DIGIT) != 0) {
            boolean neg = false;
            if (c == '-') {
                c = read();
                if (c != '.' && (c < '0' || c > '9')) {
                    peekc = c;
                    return ttype = '-';
                }
                neg = true;
            }
            double v = 0;
            int decexp = 0;
            int seendot = 0;
            while (true) {
                if (c == '.' && seendot == 0)
                    seendot = 1;
                else if ('0' <= c && c <= '9') {
                    v = v * 10 + (c - '0');
                    decexp += seendot;
                } else
                    break;
                c = read();
            }
            peekc = c;
            if (decexp != 0) {
                double denom = 10;
                decexp--;
                while (decexp > 0) {
                    denom *= 10;
                    decexp--;
                }
                /* Do one division of a likely-to-be-more-accurate number */
                v = v / denom;
            }
            nval = neg ? -v : v;
            return ttype = TT_NUMBER;
        }

        if ((ctype & CT_ALPHA) != 0) {
            int i = 0;
            do {
                if (i >= buf.length) {
                    buf = Arrays.copyOf(buf, buf.length * 2);
                }
                buf[i++] = (char) c;
                c = read();
                ctype = c < 0 ? CT_WHITESPACE : c < 256 ? ct[c] : CT_ALPHA;
            } while ((ctype & (CT_ALPHA | CT_DIGIT)) != 0);
            peekc = c;
            sval = String.copyValueOf(buf, 0, i);
            if (forceLower)
                sval = sval.toLowerCase();
            return ttype = TT_WORD;
        }

        if ((ctype & CT_QUOTE) != 0) {
            ttype = c;
            int i = 0;
            /* Invariants (because \Octal needs a lookahead):
             *   (i)  c contains char value
             *   (ii) d contains the lookahead
             */
            int d = read();
            while (d >= 0 && d != ttype && d != '\n' && d != '\r') {
                if (d == '\\') {
                    c = read();
                    int first = c;   /* To allow \377, but not \477 */
                    if (c >= '0' && c <= '7') {
                        c = c - '0';
                        int c2 = read();
                        if ('0' <= c2 && c2 <= '7') {
                            c = (c << 3) + (c2 - '0');
                            c2 = read();
                            if ('0' <= c2 && c2 <= '7' && first <= '3') {
                                c = (c << 3) + (c2 - '0');
                                d = read();
                            } else
                                d = c2;
                        } else
                          d = c2;
                    } else {
                        switch (c) {
                        case 'a':
                            c = 0x7;
                            break;
                        case 'b':
                            c = '\b';
                            break;
                        case 'f':
                            c = 0xC;
                            break;
                        case 'n':
                            c = '\n';
                            break;
                        case 'r':
                            c = '\r';
                            break;
                        case 't':
                            c = '\t';
                            break;
                        case 'v':
                            c = 0xB;
                            break;
                        }
                        d = read();
                    }
                } else {
                    c = d;
                    d = read();
                }
                if (i >= buf.length) {
                    buf = Arrays.copyOf(buf, buf.length * 2);
                }
                buf[i++] = (char)c;
            }

            /* If we broke out of the loop because we found a matching quote
             * character then arrange to read a new character next time
             * around; otherwise, save the character.
             */
            peekc = (d == ttype) ? NEED_CHAR : d;

            sval = String.copyValueOf(buf, 0, i);
            return ttype;
        }

        if (c == '/' && (slashSlashCommentsP || slashStarCommentsP)) {
            c = read();
            if (c == '*' && slashStarCommentsP) {
                int prevc = 0;
                while ((c = read()) != '/' || prevc != '*') {
                    if (c == '\r') {
                        LINENO++;
                        c = read();
                        if (c == '\n') {
                            c = read();
                        }
                    } else {
                        if (c == '\n') {
                            LINENO++;
                            c = read();
                        }
                    }
                    if (c < 0)
                        return ttype = TT_EOF;
                    prevc = c;
                }
                return nextToken();
            } else if (c == '/' && slashSlashCommentsP) {
                while ((c = read()) != '\n' && c != '\r' && c >= 0);
                peekc = c;
                return nextToken();
            } else {
                /* Now see if it is still a single line comment */
                if ((ct['/'] & CT_COMMENT) != 0) {
                    while ((c = read()) != '\n' && c != '\r' && c >= 0);
                    peekc = c;
                    return nextToken();
                } else {
                    peekc = c;
                    return ttype = '/';
                }
            }
        }

        if ((ctype & CT_COMMENT) != 0) {
            while ((c = read()) != '\n' && c != '\r' && c >= 0);
            peekc = c;
            return nextToken();
        }

        return ttype = c;
    }

    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: nextToken()
nval
sval
ttype/**
     * Causes the next call to the {@code nextToken} method of this
     * tokenizer to return the current value in the {@code ttype}
     * field, and not to modify the value in the {@code nval} or
     * {@code sval} field.
     *
     * @see     java.io.StreamTokenizer#nextToken()
     * @see     java.io.StreamTokenizer#nval
     * @see     java.io.StreamTokenizer#sval
     * @see     java.io.StreamTokenizer#ttype
     */
    public void pushBack() {
        if (ttype != TT_NOTHING)   /* No-op if nextToken() not called */
            pushedBack = true;
    }

    Return the current line number.
Returns:  the current line number of this stream tokenizer./**
     * Return the current line number.
     *
     * @return  the current line number of this stream tokenizer.
     */
    public int lineno() {
        return LINENO;
    }

    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
See Also: nval
sval
ttype
Returns:  a string representation of the token/**
     * Returns the string representation of the current stream token and
     * the line number it occurs on.
     *
     * <p>The precise string returned is unspecified, although the following
     * example can be considered typical:
     *
     * <blockquote><pre>Token['a'], line 10</pre></blockquote>
     *
     * @return  a string representation of the token
     * @see     java.io.StreamTokenizer#nval
     * @see     java.io.StreamTokenizer#sval
     * @see     java.io.StreamTokenizer#ttype
     */
    public String toString() {
        String ret;
        switch (ttype) {
          case TT_EOF:
            ret = "EOF";
            break;
          case TT_EOL:
            ret = "EOL";
            break;
          case TT_WORD:
            ret = sval;
            break;
          case TT_NUMBER:
            ret = "n=" + nval;
            break;
          case TT_NOTHING:
            ret = "NOTHING";
            break;
          default: {
                /*
                 * ttype is the first character of either a quoted string or
                 * is an ordinary character. ttype can definitely not be less
                 * than 0, since those are reserved values used in the previous
                 * case statements
                 */
                if (ttype < 256 &&
                    ((ctype[ttype] & CT_QUOTE) != 0)) {
                    ret = sval;
                    break;
                }

                char s[] = new char[3];
                s[0] = s[2] = '\'';
                s[1] = (char) ttype;
                ret = new String(s);
                break;
            }
        }
        return "Token[" + ret + "], line " + LINENO;
    }

}
Params:	is – an input stream.
See Also:	BufferedReader InputStreamReader StreamTokenizer(Reader)
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);
Params:	r – a Reader object providing the input stream.
Since:	1.1
Params:	low – the low end of the range. hi – the high end of the range.
See Also:	ordinaryChar(int)
Params:	flag – `true` indicates that end-of-line characters are separate tokens; `false` indicates that end-of-line characters are white space.
See Also:	nextToken() ttype TT_EOL
Params:	fl – `true` indicates that all word tokens should be lowercased.
See Also:	nextToken() ttype TT_WORD
Throws:	IOException – if an I/O error occurs.
See Also:	nval sval ttype
Returns:	the value of the `ttype` field.
/

java/ 15/ java.base/java/io/StreamTokenizer.java
