Package org.apache.commons.io.input

Class NullReader

  • All Implemented Interfaces:
    java.io.Closeable, java.lang.AutoCloseable, java.lang.Readable
    public class NullReader
extends java.io.Reader
    A functional, lightweight Reader that emulates a reader of a specified size.

    This implementation provides a lightweight 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
          }
      }
  }

    This class is not thread-safe.

    Since:
    1.3

    • Field Summary

      Fields 
      Modifier and Type Field Description
      static 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

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void close()
      Closes this Reader.
      long getPosition()
      Gets the current position.
      long getSize()
      Gets the size this Reader emulates.
      void mark​(int readLimit)
      Marks the current position.
      boolean markSupported()
      Tests 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

        nullReader, read, ready, transferTo

      • Methods inherited from class java.lang.Object

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

    • Field Detail

    • Constructor Detail

      • 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 Detail

      • close

        public void close()
           throws java.io.IOException
        Closes this Reader. Resets the internal state to the initial values.
        Specified by:
        close in interface java.lang.AutoCloseable
        Specified by:
        close in interface java.io.Closeable
        Specified by:
        close in class java.io.Reader
        Throws:
        java.io.IOException - If an error occurs.

      • getPosition

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

      • getSize

        public long getSize()
        Gets 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 java.io.Reader
        Parameters:
        readLimit - The number of characters before this marked position is invalid.
        Throws:
        java.lang.UnsupportedOperationException - if mark is not supported.

      • markSupported

        public boolean markSupported()
        Tests whether mark is supported.
        Overrides:
        markSupported in class java.io.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 java.io.IOException
        Reads a character.
        Overrides:
        read in class java.io.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:
        java.io.EOFException - if the end of file is reached and throwEofException is set to true.
        java.io.IOException - if trying to read past the end of file.

      • read

        public int read​(char[] chars)
         throws java.io.IOException
        Reads some characters into the specified array.
        Overrides:
        read in class java.io.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:
        java.io.EOFException - if the end of file is reached and throwEofException is set to true.
        java.io.IOException - if trying to read past the end of file.

      • read

        public int read​(char[] chars,
                int offset,
                int length)
         throws java.io.IOException
        Reads the specified number characters into an array.
        Specified by:
        read in class java.io.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:
        java.lang.NullPointerException - if the array is null.
        java.lang.IndexOutOfBoundsException - if offset or length are negative, or if offset + length is greater than chars.length.
        java.io.EOFException - if the end of file is reached and throwEofException is set to true.
        java.io.IOException - if trying to read past the end of file.

      • reset

        public void reset()
           throws java.io.IOException
        Resets the stream to the point when mark was last called.
        Overrides:
        reset in class java.io.Reader
        Throws:
        java.lang.UnsupportedOperationException - if mark is not supported.
        java.io.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 java.io.IOException
        Skips a specified number of characters.
        Overrides:
        skip in class java.io.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:
        java.io.EOFException - if the end of file is reached and throwEofException is set to true.
        java.io.IOException - if trying to read past the end of file.