Question

You need to write a program (one java class containing Main calling function isPalindrome (String str).
The function isPalindrome (returns Boolean T/F) needs to determine whether or not a string is a palindrome, using recursion.
 
The algorithm to check whether a string is a palindrome is shown below:
/* check for first and last char of String:
         * if they are same then do the same thing for a substring
         * with first and last char removed. and carry on this
         * until you string completes or condition fails
         * Function calling itself: Recursion
         */

Answer 1

`Hey,

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import java.util.*; //util package importing for scanner
public class Palindrome {

public static boolean isPalindrome(String str)
{
//test for end of recursion
if(str.length() < 2) {return true;}

//check first and last character for equality
if(str.charAt(0) != str.charAt(str.length() - 1)){return false;}

//recursion call
return isPalindrome(str.substring(1, str.length() - 1));
}
public static void main(String[] args)
{
Scanner input=new Scanner(System.in); //scanner class input object
System.out.println("Enter the string");
String input_word=input.nextLine(); //taking string from user as input
if (isPalindrome(input_word)) //calling isPalindrome() function by passing input_word as parameter
System.out.println(input_word +" is a palindrome"); //if it returns true print string is palindrome
else
System.out.println(input_word+" is not a palindrome"); //if not true print the string is not a palindrome

  
}
}

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Thanks.