Java: null in constructor

Excuse me, this question is a bit theoretical, but I want to understand it

Why do I pass null parameters to constructors? Do I get NullPointerException?

This is my example

new AttendeeDetail("Gus Goose","1151","15-01-2012",(Integer) null,null)

This is the class:

public class AttendeeDetail {

    private String ticketholder_name;
    private String user_id;
    private String date_of_birth;
    private int tickets_purchased;
    private ArrayList<Ticket> tickets;

    public AttendeeDetail(String ticketholder_name,String user_id,String date_of_birth,int tickets_purchased,ArrayList<Ticket> tickets) 
    {
        this.ticketholder_name=ticketholder_name;
        this.user_id=user_id;
        this.date_of_birth=date_of_birth;
        this.tickets_purchased=tickets_purchased;
        this.tickets=tickets;
    }
}

Solution

Int cannot be null If you do need to pass a null value, use the integer type