CODEWITHSUNDEEP
javarecursion
Derek
Derek

Reputation: 45

Palindrome checker with recursion?

I'm making a java program that checks the user's input to see if it's a palindrome. My code is below, but at the: 

if(isPalindrome() = true)
     System.out.println("You typed a palindrome!");

part I get the error saying "the left side of the assignment must be a variable." isn't it a variable? and what can I do to fix it? Any advice is appreciated!

public class PalindromeChecker
{
public static void main(String [] args)
{
    String answer;
    while(answer.equalsIgnoreCase("y"))
    {
        System.out.println("Please enter a String of characters.  I will check to see if");
        System.out.println("what you typed is a palindrome.");
        Scanner keys = new Scanner(System.in);
        String string = keys.nextLine();
        if(isPalindrome() = true)
            System.out.println("You typed a palindrome!");
        else
            System.out.println("That is not a palindrome.");
        System.out.print("Check another string? Y/N: ");
        answer = keys.next();
    }
}

public static boolean isPalindome(String string)
{
    if(string.length() <= 0)
        System.out.println("Not enough characters to check.");
    string = string.toUpperCase();
    return isPalindrome(string,0,string.length()-1);
}

private static boolean isPalindrome(String string, int last, int first)
{
    if(last <= first)
        return true;
    if(string.charAt(first) < 'A' || (string.charAt(first) > 'Z'))
        return isPalindrome(string,first + 1, last);
    if(string.charAt(last) < 'A' || (string.charAt(last) > 'Z'))
        return isPalindrome(string,first, last - 1);
    if(string.charAt(first) != string.charAt(last))
        return false;
    return isPalindrome(string,first + 1, last - 1);
}
}

Upvotes: 0

Views: 1100

Answers (3)

kosa
kosa

Reputation: 66677

Your method call should be: isPalindrome expecting String parameter:

if(isPalindome(string ))

And you don't need to do equality check because return type is anyway boolean.

Upvotes: 1

username tbd
username tbd

Reputation: 9392

Use

if(isPalindome(string)==true)

Instead.

Two changes:

1) You need to pass string to isPalindome.

2) You need to use two equal signs, not just one, for the sake of comparison.

Also, I believe you may have meant to write "isPalindrome" instead of "isPalindome"

Upvotes: 0

John Kugelman
John Kugelman

Reputation: 362137

Use double equals == for comparisons. A single equal sign = is the assignment operator.

if (isPalindrome() == true)

Or better yet, for boolean comparisons don't use == at all. It reads more like English if you just write:

if (isPalindrome())

Upvotes: 3

Related Questions