org.apache.commons.io.input
Class NullReader

java.lang.Object
  java.io.Reader
      org.apache.commons.io.input.NullReader

All Implemented Interfaces:

Closeable, Readable

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:

1.3

Version:

$Id: NullReader.java 1304052 2012-03-22 20:55:29Z ggregory $

Field Summary

Fields inherited from class java.io.Reader

lock

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.
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.

Methods inherited from class java.io.Reader

read, ready

Methods inherited from class java.lang.Object

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

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

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.

close

public void close()
           throws IOException

Close this Reader - resets the internal state to the initial values.

Specified by:

close in interface Closeable

Specified by:

close in class Reader

Throws:

IOException - If an error occurs.

mark

public void mark(int readlimit)

Mark the current position.

Overrides:

mark in class Reader

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.

Overrides:

markSupported in class Reader

Returns:

Whether mark is supported or not.

read

public int read()
         throws IOException

Read a character.

Overrides:

read in class Reader

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)
         throws IOException

Read some characters into the specified array.

Overrides:

read in class Reader

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)
         throws IOException

Read the specified number characters into an array.

Specified by:

read in class Reader

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()
           throws IOException

Reset the stream to the point when mark was last called.

Overrides:

reset in class Reader

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)
          throws IOException

Skip a specified number of characters.

Overrides:

skip in class Reader

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.

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.