Frequently Asked Java Program 02: Java Program to Check if Any String is Palindrome Without Using Reverse Method

Hello Folks,

As part of Frequently Asked Java Programs In Interviews For Freshers And Experienced,  in this post we will see a Java program to verify if a given string is palindrome without using inbuilt reverse method.

WHAT IS A PALINDROME STRING?

A palindromic string is a string that remains the same when its characters are reversed.

For Example: NAAN, AMMA AMMA etc.

Logic:

Since we can not use built in reverse method, so we will use different logic.

1. We will convert given string in to char array first.
2. Read char from char array from last index and concatenate.

Java Program:

package StringPrograms;

import java.util.Scanner;

public class PalindromeCharString {
        public static void main(String[] args) {

                // Reading string from user input
                Scanner sc = new Scanner(System.in);
                System.out.println("Please enter the string to check palindrome:");
                String inputByUser = sc.nextLine();
                
                // Closing input scanner 
                sc.close();
                
                // converting string in to char array
                char[] stringInChar = inputByUser.toCharArray();
                
        // Declaring an empty string variable to store reverse string
        String reverseInput = "";
                
        // reading char by char from end of array till first and forming a string
                for (int i = stringInChar.length - 1; i <= 0; i--) {
                        reverseInput = reverseInput + stringInChar[i];
                }

        // Printing both actual and reversed string
                System.out.println("Inout string:" + inputByUser);
                System.out.println("Reverse String:" + reverseInput);

        // Checking if given string is plaindrome
                if (inputByUser.equals(reverseInput))
                        System.out.println("Entered string is palindrome.");
                else
                        System.out.println("Entered string is not palindrome.");
        }
}

 

Output:
Please enter the string to check palindrome:
NANA
Inout string:NANA
Reverse String:ANAN
Entered string is not palindrome.
===============================================================
Please enter the string to check palindrome:
AMMA
Inout string:AMMA
Reverse String:AMMA
Entered string is palindrome.

You can run above program for multiple inputs and if it fails for any condition, let me know.

#HappyCoding