Java.io.LineNumberReader class in Java

• By default, line numbering begins at 0. This number increments at every line terminator as the data is read, and can be changed with a call to setLineNumber(int).
• Note however, that setLineNumber(int) does not actually change the current position in the stream; it only changes the value that will be returned by getLineNumber().
• A line is considered to be terminated by any one of a line feed ('\n'), a carriage return ('\r'), or a carriage return followed immediately by a linefeed.

• LineNumberReader(Reader in) : Create a new line-numbering reader, using the default input-buffer size.
• LineNumberReader(Reader in, int sz) : Create a new line-numbering reader, reading characters into a buffer of the given size.

• int getLineNumber() : Get the current line number.

  Syntax :public int getLineNumber()
  Returns:
  The current line number

• void mark(int readAheadLimit) : 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.

  Syntax :public void mark(int readAheadLimit)
            throws IOException
  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

• int read() : 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.

  Syntax :public int read()
           throws IOException
  Returns:
  The character read, or -1 if the end of the stream has been reached
  Throws:
  IOException

• int read(char[] cbuf, int off, int len) : Read characters into a portion of an array.Whenever a line terminator is read the current line number is incremented.

  Syntax :public int read(char[] cbuf,
         int off,
         int len)
           throws IOException
  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

• String readLine() : Read a line of text.Whenever a line terminator is read the current line number is incremented.

  Syntax :public String readLine()
                  throws IOException
  Returns:
  A String containing the contents of the line, not including any line 
  termination characters, or null if the end of the stream has been reached
  Throws:
  IOException

• void reset() : Reset the stream to the most recent mark.

  Syntax :public void reset()
             throws IOException
  Throws:
  IOException

• void setLineNumber(int lineNumber) : Set the current line number.

  Syntax :public void setLineNumber(int lineNumber)
  Parameters:
  lineNumber - An int specifying the line number

• long skip(long n) : Skip characters.

  Syntax :public long skip(long n)
            throws IOException
  Parameters:
  n - The number of characters to skip
  Returns:
  The number of characters actually skipped
  Throws:
  IOException
  IllegalArgumentException

//Java program demonstrating LineNumberReader methods
import java.io.FileReader;
import java.io.IOException;
import java.io.LineNumberReader;
class LineNumberReaderDemo
{
    public static void main(String[] args) throws IOException 
    {
        FileReader fr = new FileReader("file.txt");
        LineNumberReader lnr = new LineNumberReader(fr);
        char c[] = new char[20];

        //illustrating setLineNumber()
        lnr.setLineNumber(0);
        
        //illustrating set
        System.out.println(lnr.getLineNumber());
        
        //illustrating markSupported() method
        if(lnr.markSupported())
        {
            System.out.println("mark() method is supported");
            //illustrating mark method
            lnr.mark(100);
        }
        
        /*File Contents
        * This is first line
        this is second line
        This is third line
        */
        
        //skipping 19 characters
        lnr.skip(19);

        //illustrating ready() method
        if(lnr.ready())
        {
            //illustrating readLine() method
            System.out.println(lnr.readLine());

            //illustrating read(char c[],int off,int len)
            lnr.read(c);
            for (int i = 0; i <20 ; i++)
            {
                System.out.print(c[i]);
            }
            
            //illustrating reset() method
            lnr.reset();
            
            for (int i = 0; i <18 ; i++)
            {
                //illustrating read() method
                System.out.print((char)lnr.read());
            }
            int ch;
            
            //illustrating read() method
            System.out.println(lnr.readLine());
            while((ch = lnr.read())==1)
                System.out.print((char)ch);
        }
        
        //close the stream
        lnr.close();
    }
}

0
mark() method is supported
this is second line
This is third line
This is first line