A palindrome is a string that is spelled the same way forward and backward. Exam

Question

A palindrome is a string that is spelled the same way forward and backward. Examples of palindromes include "radar", "able was ere saw elba" (if blanks are ignored), and "a man a plan a canal panama". Write a Java application containing the following two methods: A non-recursive method testPalindrome1 that returns boolean value true is the string stored in a class variable s is a palindrome and false otherwise. All blanks in a string must be ignored for checking a string for being a palindrome, however the case of characters does matter. A recursive method testPalindrome2 with the same functionality as above. Put both methods into one class. Do not remove blanks from the input string in your code. The test string should be entered by the user. The result of checking it for being palindrome should be output to the screen. Name the project Hw4_1

Explanation / Answer

PalindromeCheck.java

import java.util.Scanner;

public class PalindromeCheck {

   public static void main(String[] args) {

       // Declaring variables
       String str = "";
boolean bool1,bool2;

       // Scanner Class Object is used to get the inputs entered by the user
       Scanner sc = new Scanner(System.in);

       // Getting the string entered by the user
       System.out.print("Enter a Sentence :");
       str = sc.nextLine();

       System.out.println(" :: Calling the Non recursive Method ::");
       //Calling the method by passing the string as input.
       bool1 = testPalindrome1(str);
      
      
       //based on the bool1 value the corresponding message will be displayed
       if (bool1 == true) {
           System.out.println(":: This is a Palindrome ::");
       } else {
           System.out.println(":: This is not a Palindrome ::");
       }
      
       System.out.println(" :: Calling the recursive Method ::");
       //Calling the method by passing the string as input.
       bool2 = testPalindrome2(str);
      
       //based on the bool1 value the corresponding message will be displayed
               if (bool2 == true) {
                   System.out.println(":: This is a Palindrome ::");
               } else {
                   System.out.println(":: This is not a Palindrome ::");
               }

   }

   /* This is a recursive function which calculates
   * whether the String is Palindrome or not using recursive method
   * Param:string
   * return: boolean
   */
   private static boolean testPalindrome2(String str) {
  
if(str.length() == 0 || str.length() == 1)
return true;
if(str.charAt(0) == str.charAt(str.length()-1))
return testPalindrome2(str.substring(1, str.length()-1));

return false;
   }

   /* This method will check whether the string is palindrome or not
   * If the String is Palindrome then it returns true
   * If not,It returns false
   * Param:string
   * return: boolean
   */
   private static boolean testPalindrome1(String str) {
      
       //Declaring local variables
       String revstr = "";
       int count = 0;
      
       //This for loop will reverse the string
       for (int i = 0; i < str.length(); i++) {
           revstr += str.charAt((str.length() - 1) - i);
       }

       /* This for loop will compare each character
       * in the user entered string and the reversed string
       */
       for (int i = 0; i < str.length(); i++) {
           if (str.charAt(i) != revstr.charAt(i))
               count++;
       }
      
       /* If the two strings are equal then return true
       * else return false
       */
       if (count == 0)
           return true;
       else
           return false;

   }

}

__________________________________________

Output1:

Enter a Sentence :able was ere saw elba

:: Calling the Non recursive Method ::
:: This is a Palindrome ::

:: Calling the recursive Method ::
:: This is a Palindrome ::

_____________________________________________

output2:

Enter a Sentence :radar

:: Calling the Non recursive Method ::
:: This is a Palindrome ::

:: Calling the recursive Method ::
:: This is a Palindrome ::

____________________________Thank You

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