Consider the following method

$/**$

Returns the last n characters from a given string.

@param str the given string

@param n the number of characters to take from the tail end of str

@return a string consisting of the last n characters of str

$*/$

public static String tail$($String str$,$ int n$)$

Rearrange the following lines of code to produce the method body, throwing appropriate exceptions if the arguments are not valid.