org.apache.commons.io.input

Class NullReader


public class NullReader
extends Reader

A functional, light weight Reader that emulates a reader of a specified size.

This implementation provides a light weight object for testing with an Reader where the contents don't matter.

One use case would be for testing the handling of large Reader as it can emulate that scenario without the overhead of actually processing large numbers of characters - significantly speeding up test execution times.

This implementation returns a space from the method that reads a character and leaves the array unchanged in the read methods that are passed a character array. If alternative data is required the processChar() and processChars() methods can be implemented to generate data, for example:

  public class TestReader extends NullReader {
      public TestReader(int size) {
          super(size);
      }
      protected char processChar() {
          return ... // return required value here
      }
      protected void processChars(char[] chars, int offset, int length) {
          for (int i = offset; i <32length; i++) {
              chars[i] = ... // set array value here
          }
      }
  }
 
Version:
$Revision: 463529 $
Since:
Commons IO 1.3

Field Summary

private boolean
eof
private long
mark
private boolean
markSupported
private long
position
private long
readlimit
private long
size
private boolean
throwEofException

Constructor Summary

NullReader(long size)
Create a Reader that emulates a specified size which supports marking and does not throw EOFException.
NullReader(long size, boolean markSupported, boolean throwEofException)
Create a Reader that emulates a specified size with option settings.

Method Summary

void
close()
Close this Reader - resets the internal state to the initial values.
private int
doEndOfFile()
Handle End of File.
long
getPosition()
Return the current position.
long
getSize()
Return the size this Reader emulates.
void
mark(int readlimit)
Mark the current position.
boolean
markSupported()
Indicates whether mark is supported.
protected int
processChar()
Return a character value for the read() method.
protected void
processChars(char[] chars, int offset, int length)
Process the characters for the read(char[], offset, length) method.
int
read()
Read a character.
int
read(char[] chars)
Read some characters into the specified array.
int
read(char[] chars, int offset, int length)
Read the specified number characters into an array.
void
reset()
Reset the stream to the point when mark was last called.
long
skip(long numberOfChars)
Skip a specified number of characters.

Field Details

eof

private boolean eof

mark

private long mark

markSupported

private boolean markSupported

position

private long position

readlimit

private long readlimit

size

private long size

throwEofException

private boolean throwEofException

Constructor Details

NullReader

public NullReader(long size)
Create a Reader that emulates a specified size which supports marking and does not throw EOFException.
Parameters:
size - The size of the reader to emulate.

NullReader

public NullReader(long size,
                  boolean markSupported,
                  boolean throwEofException)
Create a Reader that emulates a specified size with option settings.
Parameters:
size - The size of the reader to emulate.
markSupported - Whether this instance will support the mark() functionality.
throwEofException - Whether this implementation will throw an EOFException or return -1 when the end of file is reached.

Method Details

close

public void close()
            throws IOException
Close this Reader - resets the internal state to the initial values.

doEndOfFile

private int doEndOfFile()
            throws EOFException
Handle End of File.
Returns:
-1 if throwEofException is set to false

getPosition

public long getPosition()
Return the current position.
Returns:
the current position.

getSize

public long getSize()
Return the size this Reader emulates.
Returns:
The size of the reader to emulate.

mark

public void mark(int readlimit)
Mark the current position.
Parameters:
readlimit - The number of characters before this marked position is invalid.

markSupported

public boolean markSupported()
Indicates whether mark is supported.
Returns:
Whether mark is supported or not.

processChar

protected int processChar()
Return a character value for the read() method.

This implementation returns zero.

Returns:
This implementation always returns zero.

processChars

protected void processChars(char[] chars,
                            int offset,
                            int length)
Process the characters for the read(char[], offset, length) method.

This implementation leaves the character array unchanged.

Parameters:
chars - The character array
offset - The offset to start at.
length - The number of characters.

read

public int read()
            throws IOException
Read a character.
Returns:
Either The character value returned by processChar() or -1 if the end of file has been reached and throwEofException is set to false.

read

public int read(char[] chars)
            throws IOException
Read some characters into the specified array.
Parameters:
chars - The character array to read into
Returns:
The number of characters read or -1 if the end of file has been reached and throwEofException is set to false.

read

public int read(char[] chars,
                int offset,
                int length)
            throws IOException
Read the specified number characters into an array.
Parameters:
chars - The character array to read into.
offset - The offset to start reading characters into.
length - The number of characters to read.
Returns:
The number of characters read or -1 if the end of file has been reached and throwEofException is set to false.

reset

public void reset()
            throws IOException
Reset the stream to the point when mark was last called.

skip

public long skip(long numberOfChars)
            throws IOException
Skip a specified number of characters.
Parameters:
numberOfChars - The number of characters to skip.
Returns:
The number of characters skipped or -1 if the end of file has been reached and throwEofException is set to false.

Copyright (c) 2002-2009 Apache Software Foundation