nullpointerexception - Multiple Linked Lists in Java -

i trying create multiple linked list in java, @ 1 of lines getting nullpointerexception , unable find out reason why such error arising.

import java.util.*;  class node{ int data; node link;  public node(){     data = 0;     link = null; } }  public class ll{     static node add(node head[], int x){     node temp = new node();     system.out.println("enter value");     temp.data = new scanner(system.in).nextint();     temp.link = head[x].link;     head[x].link = temp;     return head[x];   }   public static void main(string []args){     int m =0;     int x = 0; int flag = 0;     system.out.println("enter size of index");     m = new scanner(system.in).nextint();     node []head = new node[m];     while(x<head.length){         head[x].data = 0; //error arises here          head[x].link = null;         x++;     }     system.out.println(head[0].data); //error arises here.   } } 

thats because head[x]/head[0] contains null reference.