Define a public class named Flop with a single public instance method named flip that takes no parameters and returns a Boolean. Flop should also provide a single public constructor that accepts a Boolean argument and sets the initial state of the Flop instance.

Flop maintains one piece of private state: the Boolean. Calling flip changes the Boolean from true to false or false to true and returns the old (not the new) state of the Boolean. So, for example:

Note that the internal state should be private.