java-error in null pointer exception - class

Question

PLEASE HELP ME TO FIND THIS ANSWER
NULL POINTER EXCEPTION ERROR HELP ME
on these two lines
25,83
null pointer exception please correct my code
i created a object l with reference to class linkk
to access methods in the class
but while accessing the methods in the class with different conditions
it is showing null pointer exception
i didnt finish the code due to this error im struck at this point i cant move
further
this is my post
in overflow
i have read answers in overflow but this is the
first time fr me to post a question in overflow ,
today i created a ac nd posting this question please help me frnds
import java . util.Scanner;
class node
{
int i,q;
node next;
node prev;
}
class link{
public static void main(String args[])
{
linkk l = new linkk();
l.op();
int user=0;
while(user!=10)
{Scanner a=new Scanner(System.in);
if(user==1)
{
System.out.println("\nenter data\n");
l.create(a.nextInt());
}System.out.println("\n1.create link\n2.insert beginning\n3.insert middle\n4.insert end\n5.delete data\n6.reverse");
user=a.nextInt();
}
if(user==2)
l.insertbeg();
if(user==3)
l.insertmid();
if(user==4)
l.insertend();
if(user==5)
l.del();
if(user==6)
l.reverse();
if(user==7)
l.display();
}
}
class linkk
{
node temp4;
int ch,add,cnt=0,t=0,b;
node p= new node();
node q;
node last;
node first=null;
public boolean isEmpty()
{
return first == null;
}
public void insertbeg()
{
}
public void insertmid()
{
}
public void insertend()
{
}
public void del()
{
}
public void reverse()
{
}
public void display()
{
}
public void create(int val)
{
first.i=val;
first.next=null;
cnt++;
}
public void ob()
{
}
public void op()
{
}
}

Answer 1

Your defined first as null as node first=null; and you are trying to access i with first object using first.i=val; by calling l.create(a.nextInt());.
You should initialize first as below:
node first = new node();//and then access i of it and so on.