This class is the superclass of all classes that filter output streams. These streams sit on top of an already existing output stream (the <i>underlying</i> output stream) which it uses as its basic sink of data, but possibly transforming the data along the way or providing additional functionality. <p> The class <code>FilterOutputStream</code> itself simply overrides all methods of <code>OutputStream</code> with versions that pass all requests to the underlying output stream. Subclasses of <code>FilterOutputStream</code> may further override some of these methods as well as provide additional methods and fields.