Java Program to Add two Numbers using Linked List

The Program below inserts two numbers to a Linked list and Adds them to produce the output.

 import java.io.*;  
 import java.lang.*;  
 class node  
 {  
   int data;  
   node next;  
   node prev;  
   node(int d)  
   {  
     data=d;  
     next=null;  
     prev=null;  
   }  
 }  
 class list  
 {  
   node first=null;  
   node curr=null;  
   void insert(int d)  
   {  
     node n1=new node(d);  
     curr=first;  
     if(curr==null)  
       first=n1;  
     else  
     {  
       while(curr.next!=null)  
         curr=curr.next;  
       curr.next=n1;  
     }  
   }  
   void display()  
   {  
     curr=first;  
     if(curr==null)  
       System.out.println("no list");  
     else  
     {  
       while(curr!=null)  
       {  
         System.out.print(curr.data);  
         curr=curr.next;  
       }  
     }  
   }  
 }  
 public class Sum {  
   public static void main(String[] args) {  
    DataInputStream get=new DataInputStream(System.in);  
    list l1=new list();  
    list l2=new list();  
    list l3=new list();  
    node curr1,curr2,curr3;  
    int n1,n2,n3;  
    int p,q,d,e;  
    try  
    {  
      System.out.println("Enter 1st no:");  
      n1=Integer.parseInt(get.readLine());  
      System.out.println("Enter 2nd no:");  
      n2=Integer.parseInt(get.readLine());  
      p=0;  
      while(n1>0)  
      {  
        d=n1%10;  
        p++;  
        l1.insert(d);  
        n1=n1/10;  
      }  
      n3=n2;  
      q=0;  
      while(n3>0)  
      {  
        d=n3%10;  
        q++;  
        l2.insert(d);  
        n3=n3/10;  
      }  
      while(p>q)  
      {  
        l2.insert(0);  
        p--;  
      }  
      while(q>p)  
      {  
        l1.insert(0);  
        q--;  
      }  
      e=0;  
      curr1=l1.first;  
      curr2=l2.first;  
      while(curr1!=null&&curr2!=null)  
      {  
        e=e+curr1.data+curr2.data;  
        if(e>=10)  
        {  
         d=e%10;  
         l3.insert(d);  
         e=e/10;  
        }  
        else  
        {  
          l3.insert(e);  
          e=0;  
        }  
      curr1=curr1.next;  
      curr2=curr2.next;  
      }  
      node temp=null;  
      int s=0;  
      int i,j;  
      curr3=l3.first;  
      while(curr3!=null)  
      {  
        temp=curr3;  
        s++;  
        curr3=curr3.next;  
      }  
      curr3=l3.first;  
      s=s/2;  
      for(j=0;j<s;j++)  
      {  
        i=curr3.data;  
        curr3.data=temp.data;  
        temp.data=i;  
        curr3=curr3.next;  
        temp=temp.prev;  
      }  
      System.out.println("Sum=");  
      l3.display();  
    }  
    catch(Exception k)  
    {  
      System.out.println(k.getMessage());  
    }  
   }  
 }