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 < length; i++) {
              chars[i] = ... // set array value here
          }
      }
  }
 

Since: Commons IO 1.3

Version: $Revision: 463529 $

Field Summary
booleaneof
longmark
booleanmarkSupported
longposition
longreadlimit
longsize
booleanthrowEofException
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
voidclose()
Close this Reader - resets the internal state to the initial values.
intdoEndOfFile()
Handle End of File.
longgetPosition()
Return the current position.
longgetSize()
Return the size this Reader emulates.
voidmark(int readlimit)
Mark the current position.
booleanmarkSupported()
Indicates whether mark is supported.
protected intprocessChar()
Return a character value for the read() method.
protected voidprocessChars(char[] chars, int offset, int length)
Process the characters for the read(char[], offset, length) method.
intread()
Read a character.
intread(char[] chars)
Read some characters into the specified array.
intread(char[] chars, int offset, int length)
Read the specified number characters into an array.
voidreset()
Reset the stream to the point when mark was last called.
longskip(long numberOfChars)
Skip a specified number of characters.

Field Detail

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 Detail

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 Detail

close

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

Throws: IOException If an error occurs.

doEndOfFile

private int doEndOfFile()
Handle End of File.

Returns: -1 if throwEofException is set to false

Throws: EOFException if throwEofException is set to true.

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.

Throws: UnsupportedOperationException if mark is not supported.

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()
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.

Throws: EOFException if the end of file is reached and throwEofException is set to true. IOException if trying to read past the end of file.

read

public int read(char[] chars)
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.

Throws: EOFException if the end of file is reached and throwEofException is set to true. IOException if trying to read past the end of file.

read

public int read(char[] chars, int offset, int length)
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.

Throws: EOFException if the end of file is reached and throwEofException is set to true. IOException if trying to read past the end of file.

reset

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

Throws: UnsupportedOperationException if mark is not supported. IOException If no position has been marked or the read limit has been exceed since the last position was marked.

skip

public long skip(long numberOfChars)
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.

Throws: EOFException if the end of file is reached and throwEofException is set to true. IOException if trying to read past the end of file.

Copyright (c) 2002-2011 Apache Software Foundation