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Please I have this question which is a bit theoretical, but I would like to understand it.
Why if I pass a null argument to a constructor do I get a 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;
}
}
839
Java Constructors Never Return Null.
In computer programming, a nullary constructor is a constructor that takes no arguments. Also known as a 0-argument constructor or no-argument constructors.
Note that the constructor name must match the class name, and it cannot have a return type (like void ). Also note that the constructor is called when the object is created. All classes have constructors by default: if you do not create a class constructor yourself, Java creates one for you.
== and != The comparison and not equal to operators are allowed with null in Java. This can made useful in checking of null with objects in java.
an int can't be null.
If you really need to pass a null value, use the Integer type
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