primitive question

[Adam Confino]

Hey Java Gurus,

I have a very basic, or shall I say primitive question.

I want to use an if statement to say "if there is no INT variable contained in this object, insert a new object". I think my code does not work because primitives cannot by null.

  
if(reservation.getId() == null){
			insert(reservation);}  

My question is, how would you implement this kind of logic when using a primitive?

I appreciate your time and help. Thanks.

[Paul Sturrock]

"if there is no INT variable contained in this object, insert a new object".

This is untestable. Java doesn't have the concept of undefined primitives. You would need change your type to its wrapper type and test that.

[Sebastian Janisch]

If your getId() method ties to an instance variable of type int, then it has a default value of 0.

[Zandis Murāns]

Well. Your class "Reservation" will contain that object (field) "id" all the time.

Just check the value of that ID object:

        class Reservation {

            private Integer id = null;

            public Integer getId() {
                return id;
            }

            public void setId(Integer id) {
                this.id = id;
            }

        }
        
        // create instance / field "id" will be null at this point
        Reservation reservation = new Reservation();

        // check if reservation's ID is set
        if (reservation.getId() == null)
            reservation.setId(new Integer(1));

[Adam Confino]

Every time this object is created, it will be assigned a int ID variable.

Are there any pitfalls to coding my logic this way?

  if(reservation.getId() == 0){
			insert(reservation);
		} 

[Paul Sturrock]

If your business logic can accept 0 == unset its OK. Are there any occasions where you can set the value to zero after the reservation has been inserted?

[Adam Confino]

Paul,

I'm not aware of any situations where the the value would be set to zero. Is there a safeguard you could create?

i.e. you cannot setID() to zero after the object is created

[Paul Sturrock]

You could add logic to your set method to throw an exception if someone tried. Kind of overkill. It does sound like an object rather than a primitive makes more sense if the value can be unset.

[Adam Confino]

Thanks everyone.

[Max Rahder]

Adam Confino wrote:Paul,I'm not aware of any situations where the the value would be set to zero. Is there a safeguard you could create?

If you really want to know if it's been initialized, use Integer and not a primitive. Then, by definition, if the reference is null you'll know it hasn't been initialized. Using an int is problematic since your requirements may change and 0 may become a valid initial value. If for some reason you must use an int, I'd choose a better "uninitialized" value, like -1 (if the value must be a positive value) or Integer.MIN_VALUE.