JAVA

Implement the static method declared as follows:

/**

* Returns the number of digits of {@code n}.

*

* @param n

* {@code NaturalNumber} whose digits to count

* @return the number of digits of {@code n}

* @ensures numberOfDigits = [number of digits of n]

*/

private static int numberOfDigits(NaturalNumber n) {...}

Implement the static method declared as follows:

/**

* Returns the sum of the digits of {@code n}.

*

* @param n

* {@code NaturalNumber} whose digits to add

* @return the sum of the digits of {@code n}

* @ensures sumOfDigits = [sum of the digits of n]

*/

private static int sumOfDigits(NaturalNumber n) {...}

In addition to the kernel methods, for this question (only!) you are allowed to use the NaturalNumber method add. Implement the static method declared as follows:

/**

* Returns the sum of the digits of {@code n}.

*

* @param n

* {@code NaturalNumber} whose digits to add

* @return the sum of the digits of {@code n}

* @ensures sumOfDigits = [sum of the digits of n]

*/

private static NaturalNumber sumOfDigits(NaturalNumber n) {...}

Implement the static method declared as follows:

/**

* Divides {@code n} by 2.

*

* @param n

* {@code NaturalNumber} to be divided

* @updates n

* @ensures 2 * n <= #n < 2 * (n + 1)

*/

private static void divideBy2(NaturalNumber n) {...}

Implement the static method declared as follows:

/**

* Checks whether a {@code String} is a palindrome.

*

* @param s

* {@code String} to be checked

* @return true if {@code s} is a palindrome, false otherwise

* @ensures isPalindrome = (s = rev(s))

*/

private static boolean isPalindrome(String s) {...}