{@link Line Lines} often have a set of controls, such as gain and pan, that affect
the audio signal passing through the line. Java Sound's Line objects
let you obtain a particular control object by passing its class as the
argument to a {@link Line#getControl(Control.Type) getControl} method.
Because the various types of controls have different purposes and features,
all of their functionality is accessed from the subclasses that define
each kind of control.
