Public static vs private

Question

Hi
I have 3 classes, A, B & C.
I have one variable, var, that can be used in class B and C; I have declared it in class B, and passed when I create an istance of C in B.
Then I need also to read its value in class A.
Now the ways are two (I think ...):
1. declare it as public static in class A and then use A.var in class B and C;
2. declare it as private in A and then passed to B when I create in A an istance of B and to C then I create in B an istance to C.
Considerations:
a. I don't like to declare public variables, I think is a bad way to program,
isn'it?
b. the second way is a problem when I have 10 variables (the constructors have too many parameters), right?
Could anyone help?

Answer 1

The problem is I tryied to find these answer in
Intenrnet, but I don't find anything.That's fine. That's why most of us are here.
My application works as this:
I have a main class (A) that have a main menu in
console style; from this class I create a new client
class (B) that receive commands from a server; if a
command is valid, B create an istance of C that
rappresents a trainer machine. In C I have all
workout variables (time, incline, speed ...).
By menu (in class A) i could pause the trainer and by
A and/or remote server I could ask the state of the
machine (C).
In your explanation above, I draw your attention to "instance". You are making instances of your classes. That being the case, your variables should probably be instance variables
NOT
public static int firstVariable = 0;BUT
protected int firstVariable = 0;You would then provide get and set methods to access the protected variable.
If you find yourself writing B b = new B() then you know you are dealing with an instance and you should avoid all static variables unless you really do mean "this value is the same across all Bs".
I have 8 state variables I could manage in that way.
The only way I have for now found is definite a
public static long vars in C (and use them in A e B
as C.state, C.time, ...) to avoid to pass 8
parameters when I create the istances from A to C.Assuming that C has eight variables and your design isn't done yet you can still pass an instance of C to the other objects. They don't need to have their method/constructor signatures changed when you add a new variable as your C object encapsulates it already.
>
Is right? Any other suggestion?Yes. Don't stick to "C.time" because that's what you've got so far. Instead, you should be using
C c = new C();
c.getTime();That way, the time variable is unique to the instance.