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Instance fields and objects

Tricia Lemay
Greenhorn

Joined: Sep 16, 2004
Posts: 15
Just checking to be sure I'm understanding correctly.

An instance field is a variable defined in a class. This is true.

This instance field is present in every object of the class.

The object is merely a reference to the value that is stored in the instance variable. The object is not a value in itself but just a state.

Is this correct? Or should I work on this somemore?
Svend Rost
Ranch Hand

Joined: Oct 23, 2002
Posts: 904
Hi,

Instance members are instance variables and instance methods of
an object and they can only be accessed or invoked through an
obj. reference.

The object is merely a reference to the value that is stored in the instance variable. The object is not a value in itself but just a state.


Object o = new Object();

In the line of code o is the pointer to the piece of memory representing
the object.

An object has a state which is the values of the current
instance members.

/Svend Rost
Tricia Lemay
Greenhorn

Joined: Sep 16, 2004
Posts: 15
Seems like a whole "nother" language! My head hurts! So does every object have it's own value?
Svend Rost
Ranch Hand

Joined: Oct 23, 2002
Posts: 904


I guess it depends "value". How do you define it?
Generaly I find value a bad term to use in connection with objects,
as they arn't like strings or integers.

If I make two objects

Person p1 = new Person("John");
Person p2 = new Person("Jack");

then you'd might say that they have different value.

If we then make the following:
p1 = p2;

then we can say that they have the same "value", as the two
identifiers (that is, p1 and p2) point to the same object.

Hope it helped...

/Svend Rost
Tricia Lemay
Greenhorn

Joined: Sep 16, 2004
Posts: 15
Thanx Svend,

Yes, it's helped. I don't like "value" either. Maybe I am just making the question harder than it is. (I think it is a badly worded question in the first place.

T/F

An instance field is a variable defined in a class for which every object of the class has its own value.

Well... I got a 50/50 chance on it don't I!

Edwin Keeton
Ranch Hand

Joined: Jul 10, 2002
Posts: 214

T/F

An instance field is a variable defined in a class for which every object of the class has its own value.


Ans: T

From the Sun Java tutorial:
Every time you create an instance of a class, the runtime system creates one copy of each class's instance variables for the instance.


SCJP, SCWCD
Tricia Lemay
Greenhorn

Joined: Sep 16, 2004
Posts: 15
Thanx Edwin!

 
 
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