[anonymouscodder]

So you commented this:

System.out.println("Enter a Binary Number:");//prompt for binary number to be converted

And didn't commented this?

                int r; 
                int s = 0; 
                int p = 1; 

...

[japanir]

The reson is that after checking if n is a binary number, the value of n is 0.
then the while loop to convert n to decimal will NEVER execure. because n is never bigger than 0.
you can have two options.
1. you can set a temp variable to hold the value of n, and perform the check on this variable.
2. do both checking and converting in the same loop:

option 2: - converting and checking in the same loop

import java.util.Scanner;  
public class TestClass{  
  
        public static void main(String[] args) {
        	//binary value              
 			int bin = 0;
 			//decimal value
 			int decimal = 0;
 			//Scanner object
 			Scanner s = new Scanner(System.in);
 			//the pow of 2
 			int p = 1;
 			
 			//getting binary number
 			System.out.println("Enter Binary Number");
 			bin = s.nextInt();
 			
 			//the loop - checking and converting
 			while(bin > 0){
 				int decimalDig = bin % 10;
 				if(decimalDig != 0 && decimalDig != 1){
 					System.out.println("Number is not Binary");
 					System.exit(0);
 				}
 				//converting
 				else {
 					decimal += decimalDig * p;
 					p *= 2;
 					bin /= 10;	
 				}
 			}
 			//printing decimal value
 			System.out.println("Decimal Value is: " + decimal);
        	  
        }
}

[ninechances]

you should really think about naming your variables something more straight forward.