Package org.apache.commons.io.input

Class NullInputStream

java.lang.Object
java.io.InputStream
org.apache.commons.io.input.NullInputStream
All Implemented Interfaces:
Closeable, AutoCloseable
public class NullInputStream extends InputStream
A functional, light weight InputStream that emulates a stream of a specified size.

This implementation provides a light weight object for testing with an InputStream where the contents don't matter.

One use case would be for testing the handling of large InputStream as it can emulate that scenario without the overhead of actually processing large numbers of bytes - significantly speeding up test execution times.

This implementation returns zero from the method that reads a byte and leaves the array unchanged in the read methods that are passed a byte array. If alternative data is required the processByte() and processBytes() methods can be implemented to generate data, for example: 

  public class TestInputStream extends NullInputStream {
      public TestInputStream(int size) {
          super(size);
      }
      protected int processByte() {
          return ... // return required value here
      }
      protected void processBytes(byte[] bytes, int offset, int length) {
          for (int i = offset; i < length; i++) {
              bytes[i] = ... // set array value here
          }
      }
  }
Since:
1.3

  • Field Summary

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

  • Constructor Summary

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

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    available()
    Returns the number of bytes that can be read.
    void
    close()
    Closes this input stream - resets the internal state to the initial values.
    long
    getPosition()
    Gets the current position.
    long
    getSize()
    Gets the size this InputStream emulates.
    void
    mark(int readLimit)
    Marks the current position.
    boolean
    markSupported()
    Tests whether mark is supported.
    protected int
    processByte()
    Returns a byte value for the read() method.
    protected void
    processBytes(byte[] bytes, int offset, int length)
    Processes the bytes for the read(byte[], offset, length) method.
    int
    read()
    Reads a byte.
    int
    read(byte[] bytes)
    Reads some bytes into the specified array.
    int
    read(byte[] bytes, int offset, int length)
    Reads the specified number bytes into an array.
    void
    reset()
    Resets the stream to the point when mark was last called.
    long
    skip(long numberOfBytes)
    Skips a specified number of bytes.

    Methods inherited from class java.lang.Object

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

  • Field Details

  • Constructor Details

    • NullInputStream

      public NullInputStream()
      Constructs an InputStream that emulates a size 0 stream which supports marking and does not throw EOFException.
      Since:
      2.7

    • NullInputStream

      public NullInputStream(long size)
      Constructs an InputStream that emulates a specified size which supports marking and does not throw EOFException.
      Parameters:
      size - The size of the input stream to emulate.

    • NullInputStream

      public NullInputStream(long size, boolean markSupported, boolean throwEofException)
      Constructs an InputStream that emulates a specified size with option settings.
      Parameters:
      size - The size of the input stream 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

    • available

      public int available()
      Returns the number of bytes that can be read.
      Overrides:
      available in class InputStream
      Returns:
      The number of bytes that can be read.

    • close

      public void close() throws IOException
      Closes this input stream - resets the internal state to the initial values.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Overrides:
      close in class InputStream
      Throws:
      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 InputStream emulates.
      Returns:
      The size of the input stream to emulate.

    • mark

      public void mark(int readLimit)
      Marks the current position.
      Overrides:
      mark in class InputStream
      Parameters:
      readLimit - The number of bytes before this marked position is invalid.
      Throws:
      UnsupportedOperationException - if mark is not supported.

    • markSupported

      public boolean markSupported()
      Tests whether mark is supported.
      Overrides:
      markSupported in class InputStream
      Returns:
      Whether mark is supported or not.

    • processByte

      protected int processByte()
      Returns a byte value for the read() method.

      This implementation returns zero.

      Returns:
      This implementation always returns zero.

    • processBytes

      protected void processBytes(byte[] bytes, int offset, int length)
      Processes the bytes for the read(byte[], offset, length) method.

      This implementation leaves the byte array unchanged.

      Parameters:
      bytes - The byte array
      offset - The offset to start at.
      length - The number of bytes.

    • read

      public int read() throws IOException
      Reads a byte.
      Specified by:
      read in class InputStream
      Returns:
      Either The byte value returned by processByte() 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(byte[] bytes) throws IOException
      Reads some bytes into the specified array.
      Overrides:
      read in class InputStream
      Parameters:
      bytes - The byte array to read into
      Returns:
      The number of bytes 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(byte[] bytes, int offset, int length) throws IOException
      Reads the specified number bytes into an array.
      Overrides:
      read in class InputStream
      Parameters:
      bytes - The byte array to read into.
      offset - The offset to start reading bytes into.
      length - The number of bytes to read.
      Returns:
      The number of bytes 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 InputStream
      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 numberOfBytes) throws IOException
      Skips a specified number of bytes.
      Overrides:
      skip in class InputStream
      Parameters:
      numberOfBytes - The number of bytes to skip.
      Returns:
      The number of bytes 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.