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## 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:
  Commons IO 1.3
Version:
  $Revision: 736890 $

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.

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