7.3 The OuputStream class

The OutputStream class is an abstract class from which all output streams inherit. It has several methods that are common to all output streams. These methods are:

close	Closes this output stream and releases any system resources associated with this stream.
flush	Flushes this output stream and forces any buffered output bytes to be written out.
write	Writes the specified byte to this output stream. This method is overloaded so that an array of bytes can also be written.

Some of the sub-classes of OuputStream are:

ByteArrayOuputStream - This stream allows bytes to be written to it. The contents of the stream can then be retrieved as an array of bytes.
DataOutputStream - This stream allows an application to write primitive Java data types to a stream.
FileOutputStream - This stream writes to a file.
BufferedOutputStream - This stream buffers the data written to it and writes it to another stream in blocks.

Source

Java API documentation