//TestPalindrome.java
//Determines if a string is a palindrome.

public class TestPalindrome
{
    public static void main(String[] args)
    {
        System.out.println("\nThis program tests some strings and "
            + "reports whether they are palindromes.\n");
        System.out.println("\"noon\""
            + (isPalindrome("noon", 0, "noon".length() - 1)
            ? " is " : " is not ") + "a palindrome.");
        System.out.println("\"eve\""
            + (isPalindrome("eve", 0, "eve".length() - 1)
            ? " is " : " is not ") + "a palindrome.");
        System.out.println("\"morn\""
            + (isPalindrome("morn", 0, "morn".length() - 1)
            ? " is " : " is not ") + "a palindrome.");
        System.out.println("\"ablewasiereisawelba\""
            + (isPalindrome("ablewasiereisawelba", 0,
                            "ablewasiereisawelba".length() - 1)
            ? " is " : " is not ") + "a palindrome.");
        System.out.println("\"amanaplanacanalpanama\""
            + (isPalindrome("amanaplanacanalpanama", 0,
                            "amanaplanacanalpanama".length() - 1)
            ? " is " : " is not ") + "a palindrome.");
        System.out.println("\"amanaplanacanapanama\""
            + (isPalindrome("amanaplanacanapanama", 0,
                            "amanaplanacanapanama".length() - 1)
            ? " is " : " is not ") + "a palindrome.");
    }

    public static boolean isPalindrome
    (
        String s,
        int first,
        int last
     )
    /**<
    Determine whether a string is a palindrome.
    @return true if s is a palindrome between the indices first
    and last (inclusive), false otherwise.
    @param s The full string to be tested.
    @param first The lower index of the portion of the string
    to be tested on the current call.
    @param The upper index of the portion of the string to be
    tested on the current call.
    <p>Pre:<p>s contains a non-empty string object and
    0 <= first, last <= s.length().
    Post:<p>No side effects.
    */
    {
        if (first >= last)
            return true;
        else
            return (s.charAt(first) == s.charAt(last) &&
                    isPalindrome(s, first+1, last-1));
    }
}