org.apache.commons.io

Class LineIterator

java.lang.Object

org.apache.commons.io.LineIterator

All Implemented Interfaces:

java.util.Iterator

public class LineIterator
extends java.lang.Object
implements java.util.Iterator

An Iterator over the lines in a Reader.

LineIterator holds a reference to an open Reader. When you have finished with the iterator you should close the reader to free internal resources. This can be done by closing the reader directly, or by calling the close() or closeQuietly(LineIterator) method on the iterator.

The recommended usage pattern is:

 LineIterator it = FileUtils.lineIterator(file, "UTF-8");
 try {
   while (it.hasNext()) {
     String line = it.nextLine();
     /// do something with line
   }
 } finally {
   LineIterator.closeQuietly(iterator);
 }
 

Since:

Commons IO 1.2

Version:

$Id: LineIterator.java 437567 2006-08-28 06:39:07Z bayard $

Author:

Niall Pemberton, Stephen Colebourne, Sandy McArthur

Field Summary

Fields

Modifier and Type	Field and Description
private java.io.BufferedReader	bufferedReader The reader that is being read.
private java.lang.String	cachedLine The current line.
private boolean	finished A flag indicating if the iterator has been fully read.

Constructor Summary

Constructors

Constructor and Description
LineIterator(java.io.Reader reader) Constructs an iterator of the lines for a Reader.

Method Summary

Methods

Modifier and Type	Method and Description
void	close() Closes the underlying Reader quietly.
static void	closeQuietly(LineIterator iterator) Closes the iterator, handling null and ignoring exceptions.
boolean	hasNext() Indicates whether the Reader has more lines.
protected boolean	isValidLine(java.lang.String line) Overridable method to validate each line that is returned.
java.lang.Object	next() Returns the next line in the wrapped Reader.
java.lang.String	nextLine() Returns the next line in the wrapped Reader.
void	remove() Unsupported.

Methods inherited from class java.lang.Object

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

Field Detail

bufferedReader

private final java.io.BufferedReader bufferedReader

The reader that is being read.

cachedLine

private java.lang.String cachedLine

The current line.

finished

private boolean finished

A flag indicating if the iterator has been fully read.

Constructor Detail

LineIterator

public LineIterator(java.io.Reader reader)
             throws java.lang.IllegalArgumentException

Constructs an iterator of the lines for a Reader.

Parameters:

reader - the Reader to read from, not null

Throws:

java.lang.IllegalArgumentException - if the reader is null

Method Detail

hasNext

public boolean hasNext()

Indicates whether the Reader has more lines. If there is an IOException then close() will be called on this instance.

Specified by:

hasNext in interface java.util.Iterator

Returns:

true if the Reader has more lines

Throws:

java.lang.IllegalStateException - if an IO exception occurs

isValidLine

protected boolean isValidLine(java.lang.String line)

Overridable method to validate each line that is returned.

Parameters:

line - the line that is to be validated

Returns:

true if valid, false to remove from the iterator

next

public java.lang.Object next()

Returns the next line in the wrapped Reader.

Specified by:

next in interface java.util.Iterator

Returns:

the next line from the input

Throws:

java.util.NoSuchElementException - if there is no line to return

nextLine

public java.lang.String nextLine()

Returns the next line in the wrapped Reader.

Returns:

the next line from the input

Throws:

java.util.NoSuchElementException - if there is no line to return

close

public void close()

Closes the underlying Reader quietly. This method is useful if you only want to process the first few lines of a larger file. If you do not close the iterator then the Reader remains open. This method can safely be called multiple times.

remove

public void remove()

Unsupported.

Specified by:

remove in interface java.util.Iterator

Throws:

java.lang.UnsupportedOperationException - always

closeQuietly

public static void closeQuietly(LineIterator iterator)

Closes the iterator, handling null and ignoring exceptions.

Parameters:

iterator - the iterator to close