protected FilterInputStream(InputStream in) 
{
        this.in = in;
}

Creates a FilterInputStream by assigning the argument in to the field this.in so as to remember it for later use.

Parameters:

in - the underlying input stream, or null if this instance is to be created without an underlying stream.

 public int available() throws IOException 
{
        return in.available();
}

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().

 public  void close() throws IOException 
{
        in.close();
}

Closes this input stream and releases any system resources associated with the stream. This method simply performs in.close().

 public synchronized  void mark(int readlimit) 
{
        in.mark(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).

 public boolean markSupported() 
{
        return in.markSupported();
}

Tests if this input stream supports the mark and reset methods. This method simply performs in.markSupported().

 public int read() throws IOException 
{
        return in.read();
}

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.

 public int read(byte[] b) throws IOException 
{
        return read(b, 0, b.length);
}

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.

 public int read(byte[] b,
    int off,
    int len) throws IOException 
{
        return in.read(b, off, len);
}

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.

 public synchronized  void reset() throws IOException 
{
        in.reset();
}

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.

 public long skip(long n) throws IOException 
{
        return in.skip(n);
}

Skips over and discards n bytes of data from the input stream. The skip method may, for a variety of reasons, end up skipping over some smaller number of bytes, possibly 0. The actual number of bytes skipped is returned.

This method simply performs in.skip(n).