FilterOutputStream

AI-generated Key Takeaways

• FilterOutputStream is a superclass for classes that filter output streams, adding functionality or transforming data before writing to an underlying output stream.

• It provides basic implementations of OutputStream methods, passing requests to the underlying stream, which subclasses can further override.

• Subclasses like BufferedOutputStream, DataOutputStream, and others, provide specialized filtering capabilities.

• FilterOutputStream includes methods like write, flush, and close, which interact with the underlying output stream.

• Developers can extend FilterOutputStream to create custom output stream filters tailored to specific needs.

public class FilterOutputStream extends OutputStream

Known Direct Subclasses BufferedOutputStream, CheckedOutputStream, CipherOutputStream, DataOutputStream, DeflaterOutputStream, DigestOutputStream, InflaterOutputStream, PrintStream BufferedOutputStream The class implements a buffered output stream.  CheckedOutputStream An output stream that also maintains a checksum of the data being written.  CipherOutputStream A CipherOutputStream is composed of an OutputStream and a Cipher so that write() methods first process the data before writing them out to the underlying OutputStream.  DataOutputStream A data output stream lets an application write primitive Java data types to an output stream in a portable way.  DeflaterOutputStream This class implements an output stream filter for compressing data in the "deflate" compression format.  DigestOutputStream A transparent stream that updates the associated message digest using the bits going through the stream.  InflaterOutputStream Implements an output stream filter for uncompressing data stored in the "deflate" compression format.  PrintStream A PrintStream adds functionality to another output stream, namely the ability to print representations of various data values conveniently.

Known Indirect Subclasses GZIPOutputStream, JarOutputStream, ZipOutputStream GZIPOutputStream This class implements a stream filter for writing compressed data in the GZIP file format.  JarOutputStream The JarOutputStream class is used to write the contents of a JAR file to any output stream.  ZipOutputStream This class implements an output stream filter for writing files in the ZIP file format.

This class is the superclass of all classes that filter output streams. These streams sit on top of an already existing output stream (the underlying output stream) which it uses as its basic sink of data, but possibly transforming the data along the way or providing additional functionality.

The class FilterOutputStream itself simply overrides all methods of OutputStream with versions that pass all requests to the underlying output stream. Subclasses of FilterOutputStream may further override some of these methods as well as provide additional methods and fields.

Field Summary

protected OutputStream

out

The underlying output stream to be filtered.

Public Constructor Summary

FilterOutputStream(OutputStream out) Creates an output stream filter built on top of the specified underlying output stream.

Public Method Summary

void	close() Closes this output stream and releases any system resources associated with the stream.
void	flush() Flushes this output stream and forces any buffered output bytes to be written out to the stream.
void	write(byte[] b) Writes b.length bytes to this output stream.
void	write(byte[] b, int off, int len) Writes len bytes from the specified byte array starting at offset off to this output stream.
void	write(int b) Writes the specified byte to this output stream.

Inherited Method Summary

From class java.io.OutputStream

void	close() Closes this output stream and releases any system resources associated with this stream.
void	flush() Flushes this output stream and forces any buffered output bytes to be written out.
void	write(byte[] b) Writes b.length bytes from the specified byte array to this output stream.
void	write(byte[] b, int off, int len) Writes len bytes from the specified byte array starting at offset off to this output stream.
abstract void	write(int b) Writes the specified byte to this output stream.

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

From interface java.io.Closeable

abstract void

close() Closes this stream and releases any system resources associated with it.

From interface java.io.Flushable

abstract void

flush() Flushes this stream by writing any buffered output to the underlying stream.

From interface java.lang.AutoCloseable

abstract void

close() Closes this resource, relinquishing any underlying resources.

Fields

protected OutputStream out

The underlying output stream to be filtered.

Public Constructors

public FilterOutputStream (OutputStream out)

Creates an output stream filter built on top of the specified underlying output stream.

Parameters

out	the underlying output stream to be assigned to the field this.out for later use, or null if this instance is to be created without an underlying stream.

Public Methods

public void close ()

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

The close method of FilterOutputStream calls its flush method, and then calls the close method of its underlying output stream.

Throws

IOException	if an I/O error occurs.

See Also

• flush()
• out

public void flush ()

Flushes this output stream and forces any buffered output bytes to be written out to the stream.

The flush method of FilterOutputStream calls the flush method of its underlying output stream.

Throws

IOException	if an I/O error occurs.

See Also

• out

public void write (byte[] b)

Writes b.length bytes to this output stream.

The write method of FilterOutputStream calls its write method of three arguments with the arguments b, 0, and b.length.

Note that this method does not call the one-argument write method of its underlying stream with the single argument b.

Parameters

b	the data to be written.

Throws

IOException	if an I/O error occurs.

See Also

• write(byte[], int, int)

public void write (byte[] b, int off, int len)

Writes len bytes from the specified byte array starting at offset off to this output stream.

The write method of FilterOutputStream calls the write method of one argument on each byte to output.

Note that this method does not call the write method of its underlying input stream with the same arguments. Subclasses of FilterOutputStream should provide a more efficient implementation of this method.

Parameters

b	the data.
off	the start offset in the data.
len	the number of bytes to write.

Throws

IOException	if an I/O error occurs.

See Also

• write(int)

public void write (int b)

Writes the specified byte to this output stream.

The write method of FilterOutputStream calls the write method of its underlying output stream, that is, it performs out.write(b).

Implements the abstract write method of OutputStream.

Parameters

b	the byte.

Throws

IOException	if an I/O error occurs.