Package org.apache.commons.io.input

Class NullReader

java.lang.Object
java.io.Reader
org.apache.commons.io.input.NullReader
All Implemented Interfaces:
Closeable, AutoCloseable, 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

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final NullReader
    INSTANCE
    The singleton instance.

    Fields inherited from class java.io.Reader

    lock

  • Constructor Summary

    Constructors
    Constructor
    Description
    NullReader()
    Constructs a Reader that emulates a size 0 reader which supports marking and does not throw EOFException.
    NullReader(long size)
    Constructs a Reader that emulates a specified size which supports marking and does not throw EOFException.
    NullReader(long size, boolean markSupported, boolean throwEofException)
    Constructs a Reader that emulates a specified size with option settings.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    close()
    Closes this Reader - resets the internal state to the initial values.
    long
    getPosition()
    Returns the current position.
    long
    getSize()
    Returns the size this Reader emulates.
    void
    mark(int readLimit)
    Marks the current position.
    boolean
    markSupported()
    Indicates whether mark is supported.
    protected int
    processChar()
    Returns 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()
    Reads a character.
    int
    read(char[] chars)
    Reads some characters into the specified array.
    int
    read(char[] chars, int offset, int length)
    Reads the specified number characters into an array.
    void
    reset()
    Resets the stream to the point when mark was last called.
    long
    skip(long numberOfChars)
    Skips 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

  • Field Details

    • INSTANCE

      public static final NullReader INSTANCE
      The singleton instance.
      Since:
      2.12.0

  • Constructor Details

    • NullReader

      public NullReader()
      Constructs a Reader that emulates a size 0 reader which supports marking and does not throw EOFException.
      Since:
      2.7

    • NullReader

      public NullReader(long size)
      Constructs 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)
      Constructs 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
      Closes this Reader - resets the internal state to the initial values.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Specified by:
      close in class Reader
      Throws:
      IOException - If an error occurs.

    • getPosition

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

    • getSize

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

    • mark

      public void mark(int readLimit)
      Marks 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.

    • processChar

      protected int processChar()
      Returns 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
      Reads 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
      Reads 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
      Reads 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
      Resets 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 exceeded since the last position was marked.

    • skip

      public long skip(long numberOfChars) throws IOException
      Skips 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.