adding binary numbers:java

class Node{
	
		int num;
		Node next;
	    
	    Node(int n)
	    {
	    	num=n;
	    	next = null;
	    }
	    
}   //end node

  
 class Q88
 {
 
 	
 	public static void main (String[] args)
 	{
 		
 		
 		Node head1 = toBinary(4);
		//print(head1);
		Node head2 = toBinary(2);
		//print(head2);
		
		
		double x = addBinaryNumbers(head1, head2);
		System.out.println(x);
 				
 	}//main
 	public static void print(Node top)
	    {
		while(top!=null)
		{
			System.out.printf("%d",top.num);
			top =  top.next;
		}
	    }//end print
  		public static Node toBinary(int n){
		Node np;
		Node top = null;
		Node last = null;
		
		Node xp= new Node (n);
		if (xp.num==0)return xp;
		while(n>0){
			int x = n%2;
			np = new Node(x);
			if(top==null)
				top = np;
			else 
				last.next = np;
				last = np;
				n = n/2;
		}
		return top;
		}//end function
	public static double toDecimal(Node top){
	int c = 0;
	double result = 0;
	int ans = 0;
	
	double y = Math.pow(2,2);
	
	while(top!=null)
	{
		
		result = result + (Math.pow(2,c)*top.num);	
		
		c++;
		top = top.next;
	}
	   
	return result;
}//toDecimal

	public static double addBinaryNumbers(Node top1, Node top2)
 	{
 		//declaration of variables
 		int sum = 0;
 		int carry = 0;
 		int result = 0;
 		double res = 0.0;
 		Node tail = null;
 		Node last = null;
 		Node ans  = null;
 		boolean ape = true ;
 	
 	 		while(top1!=null || top2!=null)
 		{
 			sum = top1.num + top2.num + carry;
 			System.out.println("sum" + sum);
 			carry = 0;//clear carry before next calculation
 			
 			if (sum==1 || sum == 0) 
 			{
 				
 					//System.out.println("ssssuur"+sum);
 				Node ncar = new Node (sum);
				
				if (tail==null)tail = ncar;
				else
				  last.next = ncar;
				  last = ncar;
		
				  
 			}else{
 				ans = toBinary(sum);
 				result = ans.num;
 				Node x = ans.next;
 				carry  = x.num;
 				
  				Node ncar = new Node (result);
				
				if (tail==null)tail = ncar;
				else
				  last.next = ncar;
				  last = ncar;
 				
 			}//end if;
 			
 				if ( top1.next !=null && top2.next==null) 
 			{
 				top1   = top1.next;
 				
 				System.out.println("ddddddddddddd" + top1.num);
 			}
 			
 			//get to end and both numbers are the same
 			
 			if (top1.next==null && top2.next==null && carry==1)
 			{
 				System.out.println("carrrrrrrrrrrrrr"+carry);
 				
 				Node car = new Node (carry);
 				
 				if (tail==null)tail = car;
 				else 
 					last.next = car;
 					last = car;
 				
 			}//end if
 			
 			if ( top2.next !=null && top1.next ==null) 
 		
 			{
 					top2 = top2.next;
 					System.out.println("vvvvvvvvvvvv" + top2.num);
 			}
 				
 			
 			if ( top1!=null && top2 != null)
 			{
 				System.out.println("brian");
 				top1 = top1.next;
 				top2 = top2.next;
 				
 			}
 					    
 			
 		}//while
 	/*	
 		while(tail!=null)
 		{
 			System.out.println("tail   "+tail.num);
 			tail = tail.next;
 		}
 	*/	
 		 res = toDecimal(tail); //have to send head/top
		
		return res;
 	}//addBinaryNumbers
 	
 }//class

if ( top1.next !=null && top2.next==null) 
 	{
 		top1   = top1.next;
 	}