Package org.apache.commons.io.input

Class NullInputStream

  • All Implemented Interfaces:
    java.io.Closeable, java.lang.AutoCloseable
    public class NullInputStream
extends AbstractInputStream
    A lightweight InputStream that emulates a stream of a specified size.

    This implementation provides a lightweight 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
          }
      }
  }

    This class is not thread-safe.

    Since:
    1.3

    • Field Summary

      Fields 
      Modifier and Type Field Description
      static NullInputStream INSTANCE
      Deprecated.
      Not reusable without calling init() to reset state.

    • 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

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      int available()  
      void close()
      Closes this input stream.
      long getPosition()
      Gets the current position.
      long getSize()
      Gets the size this InputStream emulates.
      NullInputStream init()
      Initializes or re-initializes this instance for reuse.
      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.io.InputStream

        nullInputStream, readAllBytes, readNBytes, readNBytes, transferTo

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • INSTANCE

        @Deprecated
public static final NullInputStream INSTANCE
        Deprecated.
        Not reusable without calling init() to reset state.
        The singleton instance.

        Since instances hold state, call init() to reuse.

        Since:
        2.12.0

    • Constructor Detail

      • NullInputStream

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

        This is an "empty" input stream.

        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 Detail

      • available

        public int available()
        Overrides:
        available in class java.io.InputStream

      • close

        public void close()
           throws java.io.IOException
        Closes this input stream.
        Specified by:
        close in interface java.lang.AutoCloseable
        Specified by:
        close in interface java.io.Closeable
        Overrides:
        close in class AbstractInputStream
        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 InputStream emulates.
        Returns:
        The size of the input stream to emulate.

      • init

        public NullInputStream init()
        Initializes or re-initializes this instance for reuse.
        Returns:
        this instance.
        Since:
        2.17.0

      • mark

        public void mark​(int readLimit)
        Marks the current position.
        Overrides:
        mark in class java.io.InputStream
        Parameters:
        readLimit - The number of bytes 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.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, never null.
        offset - The offset to start at, always non-negative.
        length - The number of bytes to process, always non-negative and at most bytes.length - offset.

      • read

        public int read()
         throws java.io.IOException
        Reads a byte.
        Specified by:
        read in class java.io.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:
        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​(byte[] bytes)
         throws java.io.IOException
        Reads some bytes into the specified array.
        Overrides:
        read in class java.io.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:
        java.lang.NullPointerException - if the byte array is null.
        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​(byte[] bytes,
                int offset,
                int length)
         throws java.io.IOException
        Reads the specified number bytes into an array.
        Overrides:
        read in class java.io.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:
        java.lang.NullPointerException - if the byte array is null.
        java.lang.IndexOutOfBoundsException - if offset or length are negative, or if offset + length is greater than bytes.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.InputStream
        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 numberOfBytes)
          throws java.io.IOException
        Skips a specified number of bytes.
        Overrides:
        skip in class java.io.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:
        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.