Question

Write a recursive method named ispalindrome that accepts a string and returns true if the string is a palindrome, or false otherwise. A string, s, is a palindrome if:

- s is an 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.

Answer 1

To check if a string is a palindrome, the ispalindrome method compares the first and last characters, and recursively calls itself with the substring excluding these characters until the string is reduced to either 0 or 1 characters, returning true if it's a palindrome or false otherwise.

Step-by-step explanation:

You are asking how to write a recursive method named ispalindrome that determines whether a given string is a palindrome. A palindrome is a word, phrase, number, or other sequence of characters that reads the same forward and backward, ignoring spaces, punctuation, and capitalization.

To implement this, the ispalindrome method would compare the first and last characters of the string. If they are equal, the method would then call itself with the substring that excludes these two characters. This process continues either until the characters do not match (in which case, it returns false), or until the string's length is either 0 or 1 (a single character or an empty string, both of which are palindromes), at which point it returns true.

Here is a general structure for the ispalindrome method:

public boolean ispalindrome(String s) {
if (s.length() == 0 || s.length() == 1) {
// Base case: empty string or single character
return true;
} else if (s.charAt(0) == s.charAt(s.length() - 1)) {
// Recursive case: check the rest of the string
return ispalindrome(s.substring(1, s.length() - 1));
} else {
// Characters do not match, not a palindrome
return false;
}
}