Package com.Ostermiller.util

Class CSVLexer

java.lang.Object
com.Ostermiller.util.CSVLexer
public class CSVLexer extends Object
Read files in comma separated value format. More information about this class is available from ostermiller.org. The use of this class is no longer recommended. It is now recommended that you use com.Ostermiller.util.CSVParser instead. That class, has a cleaner API, and methods for returning all the values on a line in a String array. CSV is a file format used as a portable representation of a database. Each line is one entry or record and the fields in a record are separated by commas. Commas may be preceded or followed by arbitrary space and/or tab characters which are ignored.

If field includes a comma or a new line, the whole field must be surrounded with double quotes. When the field is in quotes, any quote literals must be escaped by \" Backslash literals must be escaped by \\. Otherwise a backslash an the character following it will be treated as the following character, ie."\n" is equivelent to "n". Other escape sequences may be set using the setEscapes() method. Text that comes after quotes that have been closed but come before the next comma will be ignored.

Empty fields are returned as as String of length zero: "". The following line has four empty fields and two non-empty fields in it. There is an empty field on each end, and two in the middle.

,second,, ,fifth,

Blank lines are always ignored. Other lines will be ignored if they start with a comment character as set by the setCommentStart() method.

An example of how CVSLexer might be used: 

 CSVLexer shredder = new CSVLexer(System.in);
 shredder.setCommentStart("#;!");
 shredder.setEscapes("nrtf", "\n\r\t\f");
 String t;
 while ((t = shredder.getNextToken()) != null) {
           System.out.println("" + shredder.getLineNumber() + " " + t);
 }
Since:
ostermillerutils 1.00.00
Author:
Stephen Ostermiller https://ostermiller.org/contact.pl?regarding=Java+Utilities

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    AFTER
     
    static final int
    BEFORE
    lexical states
    static final int
    COMMENT
     
    static final int
    YYEOF
    This character denotes the end of file
    static final int
    YYINITIAL
     

  • Constructor Summary

    Constructors
    Constructor
    Description
    CSVLexer(InputStream in)
    Creates a new scanner.
    CSVLexer(Reader in)
    Creates a new scanner There is also a java.io.InputStream version of this constructor.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    changeDelimiter(char newDelim)
    Change this Lexer so that it uses a new delimiter.
    void
    changeQuote(char newQuote)
    Change this Lexer so that it uses a new character for quoting.
    int
    getLineNumber()
    Get the line number that the last token came from.
    String
    getNextToken()
    Resumes scanning until the next regular expression is matched, the end of input is encountered or an I/O-Error occurs.
    static void
    main(String[] args)
    Prints out tokens and line numbers from a file or System.in.
    void
    setCommentStart(String commentDelims)
    Set the characters that indicate a comment at the beginning of the line.
    void
    setEscapes(String escapes, String replacements)
    Specify escape sequences and their replacements.
    final void
    yybegin(int newState)
    Enters a new lexical state
    final char
    yycharat(int pos)
    Returns the character at position pos from the matched text.
    final void
    yyclose()
    Closes the input stream.
    final int
    yylength()
    Returns the length of the matched text region.
    void
    yypushback(int number)
    Pushes the specified amount of characters back into the input stream.
    final void
    yyreset(Reader reader)
    Resets the scanner to read from a new input stream.
    final int
    yystate()
    Returns the current lexical state.
    final String
    yytext()
    Returns the text matched by the current regular expression.

    Methods inherited from class java.lang.Object

    equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

  • Constructor Details

    • CSVLexer

      public CSVLexer(Reader in)
      Creates a new scanner There is also a java.io.InputStream version of this constructor.
      Parameters:
      in - the java.io.Reader to read input from.

    • CSVLexer

      public CSVLexer(InputStream in)
      Creates a new scanner. There is also java.io.Reader version of this constructor.
      Parameters:
      in - the java.io.Inputstream to read input from.

  • Method Details

    • main

      public static void main(String[] args)
      Prints out tokens and line numbers from a file or System.in. If no arguments are given, System.in will be used for input. If more arguments are given, the first argument will be used as the name of the file to use as input
      Parameters:
      args - program arguments, of which the first is a filename
      Since:
      ostermillerutils 1.00.00

    • changeDelimiter

      public void changeDelimiter(char newDelim) throws BadDelimiterException
      Change this Lexer so that it uses a new delimiter.

      The initial character is a comma, the delimiter cannot be changed to a quote or other character that has special meaning in CSV.

      Parameters:
      newDelim - delimiter to which to switch.
      Throws:
      BadDelimiterException - if the character cannot be used as a delimiter.
      Since:
      ostermillerutils 1.00.00

    • changeQuote

      public void changeQuote(char newQuote) throws BadQuoteException
      Change this Lexer so that it uses a new character for quoting.

      The initial character is a double quote ("), the delimiter cannot be changed to a comma or other character that has special meaning in CSV.

      Parameters:
      newQuote - character to use for quoting.
      Throws:
      BadQuoteException - if the character cannot be used as a quote.
      Since:
      ostermillerutils 1.00.00

    • setEscapes

      public void setEscapes(String escapes, String replacements)
      Specify escape sequences and their replacements. Escape sequences set here are in addition to \\ and \". \\ and \" are always valid escape sequences. This method allows standard escape sequenced to be used. For example "\n" can be set to be a newline rather than an 'n'. A common way to call this method might be:
      setEscapes("nrtf", "\n\r\t\f");
      which would set the escape sequences to be the Java escape sequences. Characters that follow a \ that are not escape sequences will still be interpreted as that character.
      The two arguemnts to this method must be the same length. If they are not, the longer of the two will be truncated.
      Parameters:
      escapes - a list of characters that will represent escape sequences.
      replacements - the list of repacement characters for those escape sequences.
      Since:
      ostermillerutils 1.00.00

    • setCommentStart

      public void setCommentStart(String commentDelims)
      Set the characters that indicate a comment at the beginning of the line. For example if the string "#;!" were passed in, all of the following lines would be comments:
       # Comment
 ; Another Comment
 ! Yet another comment
      By default there are no comments in CVS files. Commas and quotes may not be used to indicate comment lines.
      Parameters:
      commentDelims - list of characters a comment line may start with.
      Since:
      ostermillerutils 1.00.00

    • getLineNumber

      public int getLineNumber()
      Get the line number that the last token came from.

      New line breaks that occur in the middle of a token are not counted in the line number count.

      If no tokens have been returned, the line number is undefined.

      Returns:
      line number of the last token.
      Since:
      ostermillerutils 1.00.00

    • yyclose

      public final void yyclose() throws IOException
      Closes the input stream.
      Throws:
      IOException

    • yyreset

      public final void yyreset(Reader reader)
      Resets the scanner to read from a new input stream. Does not close the old reader. All internal variables are reset, the old input stream cannot be reused (internal buffer is discarded and lost). Lexical state is set to ZZ_INITIAL.
      Parameters:
      reader - the new input stream

    • yystate

      public final int yystate()
      Returns the current lexical state.

    • yybegin

      public final void yybegin(int newState)
      Enters a new lexical state
      Parameters:
      newState - the new lexical state

    • yytext

      public final String yytext()
      Returns the text matched by the current regular expression.

    • yycharat

      public final char yycharat(int pos)
      Returns the character at position pos from the matched text. It is equivalent to yytext().charAt(pos), but faster
      Parameters:
      pos - the position of the character to fetch. A value from 0 to yylength()-1.
      Returns:
      the character at position pos

    • yylength

      public final int yylength()
      Returns the length of the matched text region.

    • yypushback

      public void yypushback(int number)
      Pushes the specified amount of characters back into the input stream. They will be read again by then next call of the scanning method
      Parameters:
      number - the number of characters to be read again. This number must not be greater than yylength()!

    • getNextToken

      public String getNextToken() throws IOException
      Resumes scanning until the next regular expression is matched, the end of input is encountered or an I/O-Error occurs.
      Returns:
      the next token
      Throws:
      IOException - if any I/O-Error occurs