Package java.io

Class FilterInputStream

java.lang.Object
java.io.InputStream
java.io.FilterInputStream
All Implemented Interfaces:
Closeable, AutoCloseable
Direct Known Subclasses:
ASN1InputStream, BufferedInputStream, CheckedInputStream, CipherInputStream, CipherInputStream, DataInputStream, DeflaterInputStream, DigestInputStream, DigestInputStream, InflaterInputStream, LineNumberInputStream, MacInputStream, OpenSSLBIOInputStream, PushbackInputStream
public class FilterInputStream
extends InputStream
Wraps an existing InputStream and performs some transformation on the input data while it is being read. Transformations can be anything from a simple byte-wise filtering input data to an on-the-fly compression or decompression of the underlying stream. Input streams that wrap another input stream and provide some additional functionality on top of it usually inherit from this class.
See Also:
FilterOutputStream

  • Field Summary

    Fields
    Modifier and Type Field Description
    protected InputStream in
    The source input stream that is filtered.

  • Constructor Summary

    Constructors
    Modifier Constructor Description
    protected FilterInputStream​(InputStream in)
    Constructs a new FilterInputStream with the specified input stream as source.

  • Method Summary

    Modifier and Type Method Description
    int available()
    Returns an estimated number of bytes that can be read or skipped without blocking for more input.
    void close()
    Closes this stream.
    void mark​(int readlimit)
    Sets a mark position in this stream.
    boolean markSupported()
    Indicates whether this stream supports mark() and reset().
    int read()
    Reads a single byte from the filtered stream and returns it as an integer in the range from 0 to 255.
    int read​(byte[] buffer, int byteOffset, int byteCount)
    Reads up to byteCount bytes from this stream and stores them in the byte array buffer starting at byteOffset.
    void reset()
    Resets this stream to the last marked location.
    long skip​(long byteCount)
    Skips byteCount bytes in this stream.

    Methods inherited from class java.io.InputStream

    read

    Methods inherited from class java.lang.Object

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

  • Field Details

    • in

      protected volatile InputStream in
      The source input stream that is filtered.

  • Constructor Details

    • FilterInputStream

      protected FilterInputStream​(InputStream in)
      Constructs a new FilterInputStream with the specified input stream as source.

      Warning: passing a null source creates an invalid FilterInputStream, that fails on every method that is not overridden. Subclasses should check for null in their constructors.

      Parameters:
      in - the input stream to filter reads on.

  • Method Details

    • available

      public int available() throws IOException
      Description copied from class: InputStream
      Returns an estimated number of bytes that can be read or skipped without blocking for more input.

      Note that this method provides such a weak guarantee that it is not very useful in practice.

      Firstly, the guarantee is "without blocking for more input" rather than "without blocking": a read may still block waiting for I/O to complete — the guarantee is merely that it won't have to wait indefinitely for data to be written. The result of this method should not be used as a license to do I/O on a thread that shouldn't be blocked.

      Secondly, the result is a conservative estimate and may be significantly smaller than the actual number of bytes available. In particular, an implementation that always returns 0 would be correct. In general, callers should only use this method if they'd be satisfied with treating the result as a boolean yes or no answer to the question "is there definitely data ready?".

      Thirdly, the fact that a given number of bytes is "available" does not guarantee that a read or skip will actually read or skip that many bytes: they may read or skip fewer.

      It is particularly important to realize that you must not use this method to size a container and assume that you can read the entirety of the stream without needing to resize the container. Such callers should probably write everything they read to a ByteArrayOutputStream and convert that to a byte array. Alternatively, if you're reading from a file, File.length() returns the current length of the file (though assuming the file's length can't change may be incorrect, reading a file is inherently racy).

      The default implementation of this method in InputStream always returns 0. Subclasses should override this method if they are able to indicate the number of bytes available.

      Overrides:
      available in class InputStream
      Returns:
      the estimated number of bytes available
      Throws:
      IOException - if this stream is closed or an error occurs

    • close

      public void close() throws IOException
      Closes this stream. This implementation closes the filtered stream.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Overrides:
      close in class InputStream
      Throws:
      IOException - if an error occurs while closing this stream.

    • mark

      public void mark​(int readlimit)
      Sets a mark position in this stream. The parameter readlimit indicates how many bytes can be read before the mark is invalidated. Sending reset() will reposition this stream back to the marked position, provided that readlimit has not been surpassed.

      This implementation sets a mark in the filtered stream.

      Overrides:
      mark in class InputStream
      Parameters:
      readlimit - the number of bytes that can be read from this stream before the mark is invalidated.
      See Also:
      markSupported(), reset()

    • markSupported

      public boolean markSupported()
      Indicates whether this stream supports mark() and reset(). This implementation returns whether or not the filtered stream supports marking.
      Overrides:
      markSupported in class InputStream
      Returns:
      true if mark() and reset() are supported, false otherwise.
      See Also:
      mark(int), reset(), skip(long)

    • read

      public int read() throws IOException
      Reads a single byte from the filtered stream and returns it as an integer in the range from 0 to 255. Returns -1 if the end of this stream has been reached.
      Specified by:
      read in class InputStream
      Returns:
      the byte read or -1 if the end of the filtered stream has been reached.
      Throws:
      IOException - if the stream is closed or another IOException occurs.

    • read

      public int read​(byte[] buffer, int byteOffset, int byteCount) throws IOException
      Description copied from class: InputStream
      Reads up to byteCount bytes from this stream and stores them in the byte array buffer starting at byteOffset. Returns the number of bytes actually read or -1 if the end of the stream has been reached.
      Overrides:
      read in class InputStream
      Throws:
      IOException - if the stream is closed or another IOException occurs.

    • reset

      public void reset() throws IOException
      Resets this stream to the last marked location. This implementation resets the target stream.
      Overrides:
      reset in class InputStream
      Throws:
      IOException - if this stream is already closed, no mark has been set or the mark is no longer valid because more than readlimit bytes have been read since setting the mark.
      See Also:
      mark(int), markSupported()

    • skip

      public long skip​(long byteCount) throws IOException
      Skips byteCount bytes in this stream. Subsequent calls to read will not return these bytes unless reset is used. This implementation skips byteCount bytes in the filtered stream.
      Overrides:
      skip in class InputStream
      Parameters:
      byteCount - the number of bytes to skip.
      Returns:
      the number of bytes actually skipped.
      Throws:
      IOException - if this stream is closed or another IOException occurs.
      See Also:
      mark(int), reset()