Class: java.io.FilterInputStream

A FilterInputStream contains some other input stream, which it uses as its basic source of data, possibly transforming the data along the way or providing additional functionality. The class FilterInputStream itself simply overrides all methods of InputStream with versions that pass all requests to the contained input stream. Subclasses of FilterInputStream may further override some of these methods and may also provide additional methods and fields.
Authors:
@author Jonathan Payne
Since:
@since JDK1.0

Inheritance

Superclass tree: Implements:

Methods

  • FilterInputStreamtop

    protected FilterInputStream(InputStream in)
    Creates a FilterInputStream by assigning the argument in to the field this.in so as to remember it for later use.
    Parameters:
    @param in the underlying input stream, or null if this instance is to be created without an underlying stream.
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  • availabletop

    public int available() throws IOException
    Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking by the next caller of a method for this input stream. The next caller might be the same thread or another thread. A single read or skip of this many bytes will not block, but may read or skip fewer bytes.

    This method returns the result of in.available().

    Return:
    @return an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking.
    Exceptions:
    @exception IOException if an I/O error occurs.
    Override hierarchy:
    available from InputStream
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  • closetop

    public void close() throws IOException
    Closes this input stream and releases any system resources associated with the stream. This method simply performs in.close().
    Exceptions:
    @exception IOException if an I/O error occurs.
    See:
    @see java.io.FilterInputStream.in
    Specified by:
    close from Closeable
    Override hierarchy:
    close from InputStream
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  • marktop

    public synchronized void mark(int readlimit)
    Marks the current position in this input stream. A subsequent call to the reset method repositions this stream at the last marked position so that subsequent reads re-read the same bytes.

    The readlimit argument tells this input stream to allow that many bytes to be read before the mark position gets invalidated.

    This method simply performs in.mark(readlimit).

    Parameters:
    @param readlimit the maximum limit of bytes that can be read before the mark position becomes invalid.
    See:
    @see java.io.FilterInputStream.in
    @see java.io.FilterInputStream.reset()
    Override hierarchy:
    mark from InputStream
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  • markSupportedtop

    public boolean markSupported()
    Tests if this input stream supports the mark and reset methods. This method simply performs in.markSupported().
    Return:
    @return true if this stream type supports the mark and reset method; false otherwise.
    See:
    @see java.io.FilterInputStream.in
    @see java.io.InputStream.mark(int)
    @see java.io.InputStream.reset()
    Override hierarchy:
    markSupported from InputStream
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  • readtop

    public int read() throws IOException
    Reads the next byte of data from this input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

    This method simply performs in.read() and returns the result.

    Return:
    @return the next byte of data, or -1 if the end of the stream is reached.
    Exceptions:
    @exception IOException if an I/O error occurs.
    See:
    @see java.io.FilterInputStream.in
    Override hierarchy:
    read from InputStream
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  • readtop

    public int read(byte[] b) throws IOException
    Reads up to byte.length bytes of data from this input stream into an array of bytes. This method blocks until some input is available.

    This method simply performs the call read(b, 0, b.length) and returns the result. It is important that it does not do in.read(b) instead; certain subclasses of FilterInputStream depend on the implementation strategy actually used.

    Parameters:
    @param b the buffer into which the data is read.
    Return:
    @return the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.
    Exceptions:
    @exception IOException if an I/O error occurs.
    See:
    @see java.io.FilterInputStream.read(byte[], int, int)
    Override hierarchy:
    read from InputStream
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  • readtop

    public int read(byte[] b, int off, int len) throws IOException
    Reads up to len bytes of data from this input stream into an array of bytes. If len is not zero, the method blocks until some input is available; otherwise, no bytes are read and 0 is returned.

    This method simply performs in.read(b, off, len) and returns the result.

    Parameters:
    @param b the buffer into which the data is read.
    @param off the start offset in the destination array b
    @param len the maximum number of bytes read.
    Return:
    @return the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.
    Exceptions:
    @exception NullPointerException If b is null.
    @exception IndexOutOfBoundsException If off is negative, len is negative, or len is greater than b.length - off
    @exception IOException if an I/O error occurs.
    See:
    @see java.io.FilterInputStream.in
    Override hierarchy:
    read from InputStream
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  • resettop

    public synchronized void reset() throws IOException
    Repositions this stream to the position at the time the mark method was last called on this input stream.

    This method simply performs in.reset().

    Stream marks are intended to be used in situations where you need to read ahead a little to see what's in the stream. Often this is most easily done by invoking some general parser. If the stream is of the type handled by the parse, it just chugs along happily. If the stream is not of that type, the parser should toss an exception when it fails. If this happens within readlimit bytes, it allows the outer code to reset the stream and try another parser.

    Exceptions:
    @exception IOException if the stream has not been marked or if the mark has been invalidated.
    See:
    @see java.io.FilterInputStream.in
    @see java.io.FilterInputStream.mark(int)
    Override hierarchy:
    reset from InputStream
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  • skiptop

    public long skip(long n) throws IOException
    Skips over and discards n bytes of data from this input stream. The skip method may, for a variety of reasons, end up skipping over some smaller number of bytes, possibly 0. This may result from any of a number of conditions; reaching end of file before n bytes have been skipped is only one possibility. The actual number of bytes skipped is returned. If n is negative, no bytes are skipped.

    The skip method of this class creates a byte array and then repeatedly reads into it until n bytes have been read or the end of the stream has been reached. Subclasses are encouraged to provide a more efficient implementation of this method. For instance, the implementation may depend on the ability to seek.

    This method simply performs in.skip(n).

    Parameters:
    @param n the number of bytes to be skipped.
    Return:
    @return the actual number of bytes skipped.
    Exceptions:
    @exception IOException if the stream does not support seek, or if some other I/O error occurs.
    Override hierarchy:
    skip from InputStream
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Fields

  • in

    volatile protected InputStream in
    The input stream to be filtered.