org.apache.commons.io.input

Class NullReader

  • All Implemented Interfaces:
    Closeable, AutoCloseable, Readable


    public class NullReaderextends 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 1586350 2014-04-10 15:57:20Z ggregory $
    • Field Summary

    • Constructor Summary

      Constructors 
      Constructor and Description
      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

      Methods 
      Modifier and TypeMethod and Description
      voidclose()
      Close this Reader - resets the internal state to the initial values.
      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.
    • 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.
      • 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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