A palindrome is a string that reads the same forwards or backwards; for example dad, mom, deed (i. e., reversing a palindrome produces the same string). Write a recursive, boolean-valued method, isPalindrome that accepts a string and returns whether the string is a palindrome. A string, s, is a palindrome if:

s is the empty string or s consists of a single letter (which reads the same back or forward), or the first and last characters of s are the same, and the rest of the string (i. e., the second through next-to-last characters) form a palindrome.