Java™ Platform
Standard Ed. 6

java.io
Class LineNumberReader

java.lang.Object
  extended by java.io.Reader
      extended by java.io.BufferedReader
          extended by java.io.LineNumberReader
All Implemented Interfaces:
Closeable, Readable

public class LineNumberReader
extends BufferedReader

A buffered character-input stream that keeps track of line numbers. This class defines methods setLineNumber(int) and getLineNumber() for setting and getting the current line number respectively.

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.

Since:
JDK1.1

Field Summary
 
Fields inherited from class java.io.Reader
lock
 
Constructor Summary
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.
 
Method Summary
 int getLineNumber()
          Get the current line number.
 void mark(int readAheadLimit)
          Mark the present position in the stream.
 int read()
          Read a single character.
 int read(char[] cbuf, int off, int len)
          Read characters into a portion of an array.
 String readLine()
          Read a line of text.
 void reset()
          Reset the stream to the most recent mark.
 void setLineNumber(int lineNumber)
          Set the current line number.
 long skip(long n)
          Skip characters.
 
Methods inherited from class java.io.BufferedReader
close, markSupported, ready
 
Methods inherited from class java.io.Reader
read, read
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

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()
         throws IOException
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)
         throws IOException
Read characters into a portion of an array. Whenever a line 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

readLine

public String readLine()
                throws IOException
Read a line of text. Whenever a line terminator is read the current line number is incremented.

Overrides:
readLine in class BufferedReader
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 - If an I/O error occurs

skip

public long skip(long n)
          throws IOException
Skip characters.

Overrides:
skip in class BufferedReader
Parameters:
n - The number of characters to skip
Returns:
The number of characters actually skipped
Throws:
IOException - If an I/O error occurs
IllegalArgumentException - If n is negative

mark

public void mark(int readAheadLimit)
          throws IOException
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()
           throws IOException
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

Java™ Platform
Standard Ed. 6

Submit a bug or feature
For further API reference and developer documentation, see Java SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

Copyright © 1993, 2011, Oracle and/or its affiliates. All rights reserved.

Scripting on this page tracks web page traffic, but does not change the content in any way.