java.io
Class FilterInputStream

java.lang.Object
  |
  +--java.io.InputStream
        |
        +--java.io.FilterInputStream

Direct Known Subclasses:

BufferedInputStream, DataInputStream, LineNumberInputStream, PushbackInputStream

public class FilterInputStream

extends InputStream

Abstract class representing a filtered input stream of bytes. This class is the basis for enhancing input stream functionality. It allows multiple input stream filters to be chained together, each providing additional functionality.

Field Summary

protected InputStream

in The actual input stream.

Constructor Summary

protected

FilterInputStream(InputStream in) Creates an input stream filter.

Method Summary

int	available() Returns the number of bytes that can be read without blocking.
void	close() Closes the input stream.
void	mark(int readlimit) Marks the current position in the input stream.
boolean	markSupported() Returns true if this stream type supports mark/reset.
int	read() Reads a byte.
int	read(byte[] b) Reads into an array of bytes.
int	read(byte[] b, int off, int len) Reads into an array of bytes.
void	reset() Repositions the stream to the last marked position.
long	skip(long n) Skips bytes of input.

Methods inherited from class java.lang.Object

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

Field Detail

in

protected InputStream in

The actual input stream.

Constructor Detail

FilterInputStream

protected FilterInputStream(InputStream in)

Creates an input stream filter.

Parameters:

in - the input stream

Method Detail

read

public int read()
         throws IOException

Reads a byte. Will block if no input is available.

Specified by:

read in class InputStream

Returns:

the byte read, or -1 if the end of the stream is reached.

Throws:

IOException - If an I/O error has occurred.

read

public int read(byte[] b)
         throws IOException

Reads into an array of bytes. Blocks until some input is available.

Overrides:

read in class InputStream

Parameters:

b - the buffer into which the data is read

Returns:

the actual number of bytes read. Returns -1 when the end of the stream is reached.

Throws:

IOException - If an I/O error has occurred.

read

public int read(byte[] b,
                int off,
                int len)
         throws IOException

Reads into an array of bytes. Blocks until some input is available. This method should be overridden in a subclass for efficiency (the default implementation reads 1 byte at a time).

Overrides:

read in class InputStream

Parameters:

b - the buffer into which the data is read

off - the start offset of the data

len - the maximum number of bytes read

Returns:

the actual number of bytes read. Returns -1 when the end of the stream is reached.

Throws:

IOException - If an I/O error has occurred.

skip

public long skip(long n)
          throws IOException

Skips bytes of input.

Overrides:

skip in class InputStream

Parameters:

n - bytes to be skipped

Returns:

actual number of bytes skipped

Throws:

IOException - If an I/O error has occurred.

available

public int available()
              throws IOException

Returns the number of bytes that can be read without blocking.

Overrides:

available in class InputStream

Returns:

the number of available bytes

IOException

close

public void close()
           throws IOException

Closes the input stream. Must be called to release any resources associated with the stream.

Overrides:

close in class InputStream

Throws:

IOException - If an I/O error has occurred.

mark

public void mark(int readlimit)

Marks the current position in the input stream. A subsequent call to reset() will reposition the stream at the last marked position so that subsequent reads will re-read the same bytes. The stream promises to allow readlimit bytes to be read before the mark position gets invalidated.

Overrides:

mark in class InputStream

Parameters:

readlimit - the maximum limit of bytes allowed tobe read before the mark position becomes invalid.

reset

public void reset()
           throws IOException

Repositions the stream to the last marked position. If the stream has not been marked, or if the mark has been invalidated, an IOException is thrown. 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.

Overrides:

reset in class InputStream

Throws:

IOException - If the stream has not been marked or if the mark has been invalidated.

markSupported

public boolean markSupported()

Returns true if this stream type supports mark/reset.

Overrides:

markSupported in class InputStream

Returns:

true if this stream type supports mark/reset; false otherwise.