Question

Create a Java method findLongestPalindrome that takes a Scanner scn as its parameter and returns a String. It returns the longest token from scn that is a palindrome (if one exists) or the empty string (otherwise). (Implementation note: Use the built in isPalindrome method. This method calls for an optimization loop.)

Where the isPalindrome Method takes a String s as a parameter and returns a boolean. It returns true if s reads the same forwards and backwards, i.e., is a Palindrome, and returns false otherwise.

I only need help creating the findLongestPalindrome method, I already have the isPalindrome method.

Answer 1

import java.util.Scanner;

public class LongestPalindrome {
   public static void main(String[] args) {
       Scanner sc = new Scanner(System.in);
       System.out.println("Longest Palindrome: "+findLongestPalindrome(sc));
   }

   // takes series of words from user
   //returns longest palindrome among them
   public static String findLongestPalindrome(Scanner sc) {
       String s="";
       String longestPal="";
       while(!s.equalsIgnoreCase("Quit")){
           s=sc.nextLine();
           if(isPalindrome(s)){
               if(s.length()>longestPal.length())
                   longestPal=s;
           }
       }
       return longestPal;
   }

  
   //checks given string is palindrome or not
   public static boolean isPalindrome(String s) {
       char aC[]=s.toCharArray();
       int i=0,j=s.length()-1;
       //iterating from the both ends
       while(i<j){
           if(aC[i]!=aC[j]){
               return false;
           }
           i++;j--;
       }
       return true;
   }
}