Module java.base
Package java.io

Class LineNumberReader

  • All Implemented Interfaces:
    Closeable,AutoCloseable,Readable
    public classLineNumberReaderextendsBufferedReader
    A buffered character-input stream that keeps track of line numbers. This class defines methodssetLineNumber(int) andgetLineNumber() for setting and getting the current line number respectively.

    By default, line numbering begins at 0. This number increments at everyline terminator as the data is read, and can be changed with a call tosetLineNumber(int). Note however, thatsetLineNumber(int) does not actually change the current position in the stream; it only changes the value that will be returned bygetLineNumber().

    A line is considered to beterminated by any one of a line feed ('\n'), a carriage return ('\r'), or a carriage return followed immediately by a linefeed.

    Since:
    1.1

    • Constructor Detail

      • LineNumberReader

        public LineNumberReader​(Reader in)
        Create a new line-numbering reader, using the default input-buffer size.
        Parameters:
        in - A Reader object to provide the underlying stream

      • LineNumberReader

        public LineNumberReader​(Reader in,                        int sz)
        Create a new line-numbering reader, reading characters into a buffer of the given size.
        Parameters:
        in - A Reader object to provide the underlying stream
        sz - An int specifying the size of the buffer

    • Method Detail

      • setLineNumber

        public void setLineNumber​(int lineNumber)
        Set the current line number.
        Parameters:
        lineNumber - An int specifying the line number
        See Also:
        getLineNumber()

      • getLineNumber

        public int getLineNumber()
        Get the current line number.
        Returns:
        The current line number
        See Also:
        setLineNumber(int)

      • read

        public int read()         throwsIOException
        Read a single character.Line terminators are compressed into single newline ('\n') characters. Whenever a line terminator is read the current line number is incremented.
        Overrides:
        read in class BufferedReader
        Returns:
        The character read, or -1 if the end of the stream has been reached
        Throws:
        IOException - If an I/O error occurs

      • read

        public int read​(char[] cbuf,                int off,                int len)         throwsIOException
        Read characters into a portion of an array. Whenever aline terminator is read the current line number is incremented.
        Overrides:
        read in class BufferedReader
        Parameters:
        cbuf - Destination buffer
        off - Offset at which to start storing characters
        len - Maximum number of characters to read
        Returns:
        The number of bytes read, or -1 if the end of the stream has already been reached
        Throws:
        IOException - If an I/O error occurs
        IndexOutOfBoundsException - If an I/O error occurs

      • mark

        public void mark​(int readAheadLimit)          throwsIOException
        Mark the present position in the stream. Subsequent calls to reset() will attempt to reposition the stream to this point, and will also reset the line number appropriately.
        Overrides:
        mark in class BufferedReader
        Parameters:
        readAheadLimit - Limit on the number of characters that may be read while still preserving the mark. After reading this many characters, attempting to reset the stream may fail.
        Throws:
        IOException - If an I/O error occurs

      • reset

        public void reset()           throwsIOException
        Reset the stream to the most recent mark.
        Overrides:
        reset in class BufferedReader
        Throws:
        IOException - If the stream has not been marked, or if the mark has been invalidated