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.
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