Re: NullPointerException!!!

//template for checking combinations of card

import javax.swing.*;
public class template {
    public static void main(String[] args)
    {
        Card handCard[] = new Card[5];
        for(int i=0;i<5;i++)
        {
            handCard[i].num = 1 + (int)(Math.random( ) * 13);
            handCard[i].suit = 1 + (int)(Math.random( ) * 4);
            System.out.println(handCard[i].num);
            System.out.println(handCard[i].suit);
        }
        System.exit(0);
    }

    public static class Card
    {
        Card(int n, int s)
        {
            n = 0;
            s = 0;
        }
        public int num = 0;
        public int suit =0;
    }
}
==============================


java.lang.NullPointerException
        at template.main(template.java:10)
Exception in thread "main"


===============================

-----------------------------------------------------------
//from sun's website
Thrown when an application attempts to use null in a case where an
object is required. These include:
Calling the instance method of a null object.
Accessing or modifying the field of a null object.
Taking the length of null as if it were an array.
Accessing or modifying the slots of null as if it were an array.
Throwing null as if it were a Throwable value.
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i found those information from sun's website but still don't
understand it
could anyone give me an example when NullPointerException been thrown?