Java Runtime Error

Question

I am new to Java. I am trying to use objects as array but it is showing a runtime error as " Null pointer exception".

This is my code :

import java.util.*;
class Students
{
String name;
int id;
double ptr;
public void show()
{
System.out.println("ID : " + id + "Name : " + name + "Pointer " + ptr);
}

}
public class Test
{

public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
Students s[] = new Students[4];

System.out.print("Enter name : ");
s[0].name = sc.nextLine();
System.out.print("Enter ID number : ");
s[0].id = sc.nextInt();
System.out.print("Enter Pointer of the student : ");
s[0].ptr = sc.nextDouble();

System.out.println(s[0].name);
}
}

Answer 1

Students[] s = new Students[4];
//every index in s is null
//so here we create the objects
for(int i=0;i<s.length;i++){
s[i] = new Students();
}

Answer 2

You didn't obtain a memory for objects you just reversed 4 pointer to Students
like
Students a1,a2,a3,a4;
each on is pointing to nu
you have to add this
for(int i=0;i<4;i++)
d[i]=new Students();