Question

Write a recursive method that tests whether a string is a palindrome. It should return a boolean T or F depending on whether or not the string is a palindrome,

Answer 1

Answer:

// program in java.

// library

import java.util.*;

// class definition

class Main

{

// recursive function to check palindrome

   public static boolean isPalin(String str){

// base case

     if(str.length() == 0 ||str.length()==1){

        return true;

     }

// if first character is equal to last

     if(str.charAt(0) == str.charAt(str.length()-1))

     {

     // recursive call

        return isPalin(str.substring(1, str.length()-1));

     }

     // return

     return false;

  }

  // main method of the class

public static void main (String[] args) throws java.lang.Exception

{

   try{

    // object to read input

Scanner scr=new Scanner(System.in);

System.out.print("Enter a string:");

 // read string from user

String myString =scr.nextLine();

 // call function to check palindrome

     if (isPalin(myString)){

        System.out.println("Given String is a palindrome");

     }

// if string is not palindrome

     else{

        System.out.println("Given String is not a palindrome");

     }    

   }catch(Exception ex){

       return;}

}

}

Explanation:

Read a string from user and assign it to variable "myString" with scanner object. Call the method isPalindrome() with string input parameter.In this method, if  length of string is 0 or 1 then it will return true(base case) otherwise it will call itself and compare first character with last character.If string is palindrome then function will return true else return false.

Output:

Enter a string:ababa                                                                                                      

Given String is a palindrome