Class LineNumberReader

All Implemented Interfaces:
Closeable, AutoCloseable, 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:
1.1

Fields

Fields declared in class java.io.Reader

lock

Constructors

Constructor Description
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.

Methods

Modifier and Type Method Description
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 declared in class java.io.BufferedReader

lines, markSupported, ready

Methods declared in class java.io.Reader

close, nullReader, read, read, transferTo

Methods declared in class java.lang.Object

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

Constructors

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

Methods

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
IndexOutOfBoundsException - 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
See Also:
Files.readAllLines(java.nio.file.Path, java.nio.charset.Charset)

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

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
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https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/io/LineNumberReader.html