Class FilterInputStream

java.lang.Object

java.io.InputStream

java.io.FilterInputStream

All Implemented Interfaces:

Closeable, AutoCloseable

Direct Known Subclasses:

BufferedInputStream, CheckedInputStream, CipherInputStream, DataInputStream, DeflaterInputStream, DigestInputStream, InflaterInputStream, LineNumberInputStream, ProgressMonitorInputStream, PushbackInputStream

public class FilterInputStream
extends InputStream

A FilterInputStream wraps 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 select methods of InputStream with versions that pass all requests to the wrapped input stream. Subclasses of FilterInputStream may of course override any methods declared or inherited by FilterInputStream, and may also provide additional fields and methods.

Since:

1.0

Field Summary

Fields

Modifier and Type	Field	Description
protected InputStream	in	The input stream to be filtered.

Constructor Summary

Constructors

Modifier	Constructor	Description
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.

Method Summary

Modifier and Type	Method	Description
int	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.
void	close()	Closes this input stream and releases any system resources associated with the stream.
void	mark(int readlimit)	Marks the current position in this input stream.
boolean	markSupported()	Tests if this input stream supports the mark and reset methods.
int	read()	Reads the next byte of data from the input stream.
int	read(byte[] b)	Reads up to b.length bytes of data from this input stream into an array of bytes.
int	read(byte[] b, int off, int len)	Reads up to len bytes of data from this input stream into an array of bytes.
void	reset()	Repositions this stream to the position at the time the mark method was last called on this input stream.
long	skip(long n)	Skips over and discards n bytes of data from the input stream.

Methods declared in class InputStream

nullInputStream, readAllBytes, readNBytes, readNBytes, skipNBytes, transferTo

Modifier and Type	Method	Description
static InputStream	nullInputStream()	Returns a new InputStream that reads no bytes.
byte[]	readAllBytes()	Reads all remaining bytes from the input stream.
int	readNBytes(byte[] b, int off, int len)	Reads the requested number of bytes from the input stream into the given byte array.
byte[]	readNBytes(int len)	Reads up to a specified number of bytes from the input stream.
void	skipNBytes(long n)	Skips over and discards exactly n bytes of data from this input stream.
long	transferTo(OutputStream out)	Reads all bytes from this input stream and writes the bytes to the given output stream in the order that they are read.

Methods declared in class Object

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

Modifier and Type	Method	Description
protected Object	clone()	Answers a new instance of the same class as the receiver, whose slots have been filled in with the values in the slots of the receiver.
boolean	equals(Object o)	Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. May cause performance issues, deadlocks and hangs.
final Class<? extends Object>	getClass()	Answers the unique instance of java.lang.Class which represents the class of the receiver.
int	hashCode()	Answers an integer hash code for the receiver.
final void	notify()	Causes one thread which is waiting on the receiver to be made ready to run.
final void	notifyAll()	Causes all threads which are waiting on the receiver to be made ready to run.
String	toString()	Answers a string containing a concise, human-readable description of the receiver.
final void	wait()	Causes the thread which sent this message to be made not ready to run pending some change in the receiver (as indicated by notify or notifyAll).
final void	wait(long time)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.
final void	wait(long time, int frac)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.

Field Details

in

protected volatile InputStream in

The input stream to be filtered.

Constructor Details

FilterInputStream

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:

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

Method Details

read

public int read()
         throws IOException

Reads the next byte of data from the 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.

Specified by:

read in class InputStream

Implementation Requirements:

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

Returns:

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

Throws:

IOException - if an I/O error occurs.

See Also:

• in

read

public int read(byte[] b)
         throws IOException

Reads up to b.length bytes of data from this input stream into an array of bytes. This method blocks until some input is available.

Overrides:

read in class InputStream

Implementation Requirements:

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:

b - the buffer into which the data is read.

Returns:

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.

Throws:

IOException - if an I/O error occurs.

See Also:

• read(byte[], int, int)

read

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.

Overrides:

read in class InputStream

Implementation Requirements:

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

Parameters:

b - the buffer into which the data is read.

off - the start offset in array b at which the data is written.

len - the maximum number of bytes to read.

Returns:

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.

Throws:

NullPointerException - If b is null.

IndexOutOfBoundsException - If off is negative, len is negative, or len is greater than b.length - off

IOException - if an I/O error occurs.

See Also:

• in

skip

public long skip(long n)
          throws IOException

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.

Overrides:

skip in class InputStream

Implementation Requirements:

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

Parameters:

n - the number of bytes to be skipped.

Returns:

the actual number of bytes skipped.

Throws:

IOException - if in.skip(n) throws an IOException.

See Also:

• InputStream.skipNBytes(long)

available

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.

Overrides:

available in class InputStream

Implementation Requirements:

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

Returns:

an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking.

Throws:

IOException - if an I/O error occurs.

close

public void close()
           throws IOException

Closes this input stream and releases any system resources associated with the stream.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Overrides:

close in class InputStream

Implementation Requirements:

This method simply performs in.close().

Throws:

IOException - if an I/O error occurs.

See Also:

• in

mark

public 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.

Overrides:

mark in class InputStream

Implementation Requirements:

This method simply performs in.mark(readlimit).

Parameters:

readlimit - the maximum limit of bytes that can be read before the mark position becomes invalid.

See Also:

• in
• reset()

reset

public void reset()
           throws IOException

Repositions this stream to the position at the time the mark method was last called on this input stream.

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

Implementation Requirements:

This method simply performs in.reset().

Throws:

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

See Also:

• in
• mark(int)

markSupported

public boolean markSupported()

Tests if this input stream supports the mark and reset methods.

Overrides:

markSupported in class InputStream

Implementation Requirements:

This method simply performs in.markSupported().

Returns:

true if this stream type supports the mark and reset method; false otherwise.

See Also:

• in
• InputStream.mark(int)
• InputStream.reset()