java program to check palindrome string using Stack, Queue, for or while loop

In this tutorial we will see programs to check whether the given String is Palindrome or not. Following are the ways to do it.
1) Using Stack
2) Using Queue
3) Using for/while loop

Program 1: Palindrome check Using Stack

import java.util.Stack;
import java.util.Scanner;
class PalindromeTest {

    public static void main(String[] args) {

    	System.out.print("Enter any string:");
        Scanner in=new Scanner(System.in);
        String inputString = in.nextLine();
        Stack stack = new Stack();

        for (int i = 0; i < inputString.length(); i++) {
            stack.push(inputString.charAt(i));
        }

        String reverseString = "";

        while (!stack.isEmpty()) {
            reverseString = reverseString+stack.pop();
        }

        if (inputString.equals(reverseString))
            System.out.println("The input String is a palindrome.");
        else
            System.out.println("The input String is not a palindrome.");

    }
}

Output 1:

Enter any string:abccba
The input String is a palindrome.

Output 2:

Enter any string:abcdef
The input String is not a palindrome.

Program 2: Palindrome check Using Queue

import java.util.Queue;
import java.util.Scanner;
import java.util.LinkedList;
class PalindromeTest {

    public static void main(String[] args) {

    	System.out.print("Enter any string:");
        Scanner in=new Scanner(System.in);
        String inputString = in.nextLine();
        Queue queue = new LinkedList();

        for (int i = inputString.length()-1; i >=0; i--) {
            queue.add(inputString.charAt(i));
        }

        String reverseString = "";

        while (!queue.isEmpty()) {
            reverseString = reverseString+queue.remove();
        }
        if (inputString.equals(reverseString))
            System.out.println("The input String is a palindrome.");
        else
            System.out.println("The input String is not a palindrome.");

    }
}

Output 1:

Enter any string:xyzzyx
xyzzyx
The input String is a palindrome.

Output 2:

Enter any string:xyz
The input String is not a palindrome.

Program 3: Using for loop/While loop and String function charAt

import java.util.Scanner;
class PalindromeTest {
   public static void main(String args[])
   {
      String reverseString="";
      Scanner scanner = new Scanner(System.in);

      System.out.println("Enter a string to check if it is a palindrome:");
      String inputString = scanner.nextLine();

      int length = inputString.length();

      for ( int i = length - 1 ; i >= 0 ; i-- )
         reverseString = reverseString + inputString.charAt(i);

      if (inputString.equals(reverseString))
         System.out.println("Input string is a palindrome.");
      else
         System.out.println("Input string is not a palindrome.");

   }
}

Output 1:

Enter a string to check if it is a palindrome:
aabbaa
Input string is a palindrome.

Output 2:

Enter a string to check if it is a palindrome:
aaabbb
Input string is not a palindrome.

If you wanna use While Loop in above program then replace the for loop with this code:

int i = length-1;
while ( i >= 0){
    reverseString = reverseString + inputString.charAt(i);
    i--;
}