OutputStream

AI-generated Key Takeaways

• OutputStream is an abstract class that represents a stream of bytes for writing data to various destinations.

• Subclasses of OutputStream need to implement the write method to handle the actual writing of bytes.

• This class provides methods for closing the stream (close), flushing buffered data (flush), and writing byte arrays (write).

• It serves as a foundation for diverse output operations like writing to files, byte arrays, and other data sinks.

• Several known direct and indirect subclasses extend OutputStream to offer specialized functionalities, such as buffered output, data compression, and encryption.

public abstract class OutputStream extends Object
implements Closeable Flushable

Known Direct Subclasses ByteArrayOutputStream, FileOutputStream, FilterOutputStream, ObjectOutputStream, PipedOutputStream ByteArrayOutputStream This class implements an output stream in which the data is written into a byte array.  FileOutputStream A file output stream is an output stream for writing data to a File or to a FileDescriptor.  FilterOutputStream This class is the superclass of all classes that filter output streams.  ObjectOutputStream An ObjectOutputStream writes primitive data types and graphs of Java objects to an OutputStream.  PipedOutputStream Places information on a communications pipe.

Known Indirect Subclasses BufferedOutputStream, CheckedOutputStream, CipherOutputStream, DataOutputStream, DeflaterOutputStream, DigestOutputStream, GZIPOutputStream, InflaterOutputStream, JarOutputStream, PrintStream, ZipOutputStream 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.  GZIPOutputStream This class implements a stream filter for writing compressed data in the GZIP file format.  InflaterOutputStream Implements an output stream filter for uncompressing data stored in the "deflate" compression format.  JarOutputStream The JarOutputStream class is used to write the contents of a JAR file to any output stream.  PrintStream A PrintStream adds functionality to another output stream, namely the ability to print representations of various data values conveniently.  ZipOutputStream This class implements an output stream filter for writing files in the ZIP file format.

This abstract class is the superclass of all classes representing an output stream of bytes. An output stream accepts output bytes and sends them to some sink.

Applications that need to define a subclass of OutputStream must always provide at least a method that writes one byte of output.

See Also

• BufferedOutputStream
• ByteArrayOutputStream
• DataOutputStream
• FilterOutputStream
• InputStream
• write(int)

Public Constructor Summary

OutputStream()

Public Method Summary

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.

Inherited Method Summary

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.

Public Constructors

public OutputStream ()

Public Methods

public void close ()

Closes this output stream and releases any system resources associated with this stream. The general contract of close is that it closes the output stream. A closed stream cannot perform output operations and cannot be reopened.

The close method of OutputStream does nothing.

Throws

IOException	if an I/O error occurs.

public void flush ()

Flushes this output stream and forces any buffered output bytes to be written out. The general contract of flush is that calling it is an indication that, if any bytes previously written have been buffered by the implementation of the output stream, such bytes should immediately be written to their intended destination.

If the intended destination of this stream is an abstraction provided by the underlying operating system, for example a file, then flushing the stream guarantees only that bytes previously written to the stream are passed to the operating system for writing; it does not guarantee that they are actually written to a physical device such as a disk drive.

The flush method of OutputStream does nothing.

Throws

IOException	if an I/O error occurs.

public void write (byte[] b)

Writes b.length bytes from the specified byte array to this output stream. The general contract for write(b) is that it should have exactly the same effect as the call write(b, 0, b.length).

Parameters

b	the data.

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 general contract for write(b, off, len) is that some of the bytes in the array b are written to the output stream in order; element b[off] is the first byte written and b[off+len-1] is the last byte written by this operation.

The write method of OutputStream calls the write method of one argument on each of the bytes to be written out. Subclasses are encouraged to override this method and provide a more efficient implementation.

If b is null, a NullPointerException is thrown.

If off is negative, or len is negative, or off+len is greater than the length of the array b, then an IndexOutOfBoundsException is thrown.

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. In particular, an IOException is thrown if the output stream is closed.

public abstract void write (int b)

Writes the specified byte to this output stream. The general contract for write is that one byte is written to the output stream. The byte to be written is the eight low-order bits of the argument b. The 24 high-order bits of b are ignored.

Subclasses of OutputStream must provide an implementation for this method.

Parameters

b	the byte.

Throws

IOException	if an I/O error occurs. In particular, an IOException may be thrown if the output stream has been closed.