When people enter their telephone numbers into a form they use many different formats. Some examples are:

(444) 999-1234 4449991234 444.999.1234In the

`PhoneNumbers`

class below, complete the
`cleanNumber`

method. It takes a string and extracts the numeric
digits from the string. If there are exactly 10 numeric digits, the number is
reformatted: `(###) ###-####`

and returned. If there are any other
number of digits, the string `"Error"`

is returned.
Hint: Use the `Character.isDigit`

method to check whether a
character is a digit.