Package org.apache.commons.io.input

Class ReversedLinesFileReader

java.lang.Object

org.apache.commons.io.input.ReversedLinesFileReader

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

public class ReversedLinesFileReader
extends java.lang.Object
implements java.io.Closeable

Reads lines in a file reversely (similar to a BufferedReader, but starting at the last line). Useful for e.g. searching in log files.

Since:

2.2

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private class	ReversedLinesFileReader.FilePart

Field Summary

Fields

Modifier and Type	Field	Description
private int	avoidNewlineSplitBufferSize
private int	blockSize
private int	byteDecrement
private ReversedLinesFileReader.FilePart	currentFilePart
private java.nio.charset.Charset	encoding
private byte[][]	newLineSequences
private java.io.RandomAccessFile	randomAccessFile
private long	totalBlockCount
private long	totalByteLength
private boolean	trailingNewlineOfFileSkipped

Constructor Summary

Constructors

Constructor	Description
ReversedLinesFileReader(java.io.File file)	Creates a ReversedLinesFileReader with default block size of 4KB and the platform's default encoding.
ReversedLinesFileReader(java.io.File file, int blockSize, java.lang.String encoding)	Creates a ReversedLinesFileReader with the given block size and encoding.
ReversedLinesFileReader(java.io.File file, int blockSize, java.nio.charset.Charset encoding)	Creates a ReversedLinesFileReader with the given block size and encoding.

Method Summary

Modifier and Type	Method	Description
void	close()	Closes underlying resources.
java.lang.String	readLine()	Returns the lines of the file from bottom to top.

Methods inherited from class java.lang.Object

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

Field Detail

blockSize

private final int blockSize

encoding

private final java.nio.charset.Charset encoding

randomAccessFile

private final java.io.RandomAccessFile randomAccessFile

totalByteLength

private final long totalByteLength

totalBlockCount

private final long totalBlockCount

newLineSequences

private final byte[][] newLineSequences

avoidNewlineSplitBufferSize

private final int avoidNewlineSplitBufferSize

byteDecrement

private final int byteDecrement

currentFilePart

private ReversedLinesFileReader.FilePart currentFilePart

trailingNewlineOfFileSkipped

private boolean trailingNewlineOfFileSkipped

Constructor Detail

ReversedLinesFileReader

public ReversedLinesFileReader(java.io.File file)
                        throws java.io.IOException

Creates a ReversedLinesFileReader with default block size of 4KB and the platform's default encoding.

Parameters:

file - the file to be read

Throws:

java.io.IOException - if an I/O error occurs

ReversedLinesFileReader

public ReversedLinesFileReader(java.io.File file,
                               int blockSize,
                               java.nio.charset.Charset encoding)
                        throws java.io.IOException

Creates a ReversedLinesFileReader with the given block size and encoding.

Parameters:

file - the file to be read

blockSize - size of the internal buffer (for ideal performance this should match with the block size of the underlying file system).

encoding - the encoding of the file

Throws:

java.io.IOException - if an I/O error occurs

Since:

2.3

ReversedLinesFileReader

public ReversedLinesFileReader(java.io.File file,
                               int blockSize,
                               java.lang.String encoding)
                        throws java.io.IOException

Creates a ReversedLinesFileReader with the given block size and encoding.

Parameters:

file - the file to be read

blockSize - size of the internal buffer (for ideal performance this should match with the block size of the underlying file system).

encoding - the encoding of the file

Throws:

java.io.IOException - if an I/O error occurs

java.nio.charset.UnsupportedCharsetException - thrown instead of UnsupportedEncodingException in version 2.2 if the encoding is not supported.

Method Detail

readLine

public java.lang.String readLine()
                          throws java.io.IOException

Returns the lines of the file from bottom to top.

Returns:

the next line or null if the start of the file is reached

Throws:

java.io.IOException - if an I/O error occurs

close

public void close()
           throws java.io.IOException

Closes underlying resources.

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface java.io.Closeable

Throws:

java.io.IOException - if an I/O error occurs