e. The <code>implements</code>
clause follows the <code>extends</code> clause if there is one. If there is
no <code>extends</code> clause, then the <code>implements</code> clause
follows the class name. The <code>implements</code> clause is optional.
<p>
For example, imagine an interface named Arithmetic that defines methods
named <code>add()</code>, <code>subtract()</code> and so on. Our ImaginaryNumber
class can declare that it implements the Arithmetic interface, thereby
guaranteeing that it provides imp