JAVA program to check whether the given number is a palindrome or not

This JAVA program is to check whether the given number is a palindrome or not. For example 121 is a palindromic number. As when you reverse 121 you get the same number.

Logic

We use the same reverse logic which we used in the program to reverse a number. Once we find the reverse of a number just compare it to the original number. If it matches then the number is a palindromic number else it is not.

Dry Run of the Program

Take input ‘n’. Let us take n=121

Keep a copy of n in originalNum i.e. originalNum=121

1st iteration while(n!=0) i.e. while(121!=0)

remainder=n%10  i.e.  remainder =121%10  hence remainder=1

reversedNum=reversedNum*10+remainder  i.e. reverse=0*10+1 hence reversedNum=1

n=n/10  i.e.  n=121/10  hence n=12

2nd iteration while(n!=0) i.e. while(12!=0)

remainder=n%10  i.e.  remainder =12%10  hence remainder=2

reversedNum=reversedNum*10+remainder  i.e. reversedNum=1*10+2 i.e. reverse=10+2 hence reversedNum=12

n=n/10  i.e.  n=12/10  hence n=1

3rd iteration while(n!=0) i.e. while(1!=0)

remainder=n%10  i.e.  remainder =1%10  hence remainder=1

reversedNum=reversedNum*10+remainder  i.e. reverse=12*10+1 i.e. reverse=120+1 hence reversedNum=121

n=n/10  i.e.  n=1/10  hence n=0

While Loop ends here as n=0.

Check if the IF condition is satisfied.

if(originalNum==reversedNum) i.e. if(121==121)

The condition is true.

Hence the number is a palindromic number.

Program

import java.util.*;
 
class palindromeNum
{
	public static void main(String args[])
	{
    		int n,reversedNum=0,remainder,originalNum;
		Scanner sc = new Scanner(System.in);
		System.out.println("Enter a number");
    		n=sc.nextInt();
		originalNum = n;
		while(n!=0)
    		{
		        remainder=n%10;
        		reversedNum=reversedNum*10+remainder;
        		n=n/10;
    		}
	    	
		if (originalNum==reversedNum)
    		{
        		System.out.println(originalNum+" is a palindrome");
    		}
    		else
    		{
        		System.out.println(originalNum+" is not a palindrome");
    		}		
	}
}

Output