Just a wild guess:

I guess there is a delay for when all parent's inherited fields and/or methods are finally available for a child class!

Take a look at this Wikipedia's article -> Lazy_initialization

However, if you enclose xpos = 1 between curly bracers like below, it works alright:

1.     {       
2.         xpos = 1;
3.     }

It forces the inheritance process to occur much earlier!

you cannot reassign the values like this..ideally in java, these two classes would be in different files.You have access to default,public and protected members but you cannot reassign them like this. Polymorphism and overriding works on instance methods, not variables.

you could do something like this to increase the xpos value

1. public float increaseXPos(){
2.   xpos=xpos+1;
3.   return xpos;
4. }
5.  
6.  void print() {
7.   println("x "+ increaseXPos());
8.   println("y "+ypos);
9.  
10.  }

how come i just cant say xpos = 1; in the extended class like this ?

The short answer is that this is not permitted by Java. Initialisation of parent class attributes from a child class must be done inside a method.

thank you all for the quick answers, i think i undersand now :D

must admit its quite hard to understand and think in OO, any good sites or tutorials that you can recomend ?

Merry Xmass all

//bre

Has any1 tested my solution of encasing an inherited parent field w/ curly bracers??? 

class Parent {
    float xpos=5;
    float ypos=8;
}

class Test extends Parent {

    // why can't I do it this way?
    {
        xpos = 100;  //  <---   force an early initialization
        //          even before constructor!!!
    }

    Test() {

        println("xpos is already = " + xpos + " before getting here!!!");
        println("even parent's xpos is set -> " + super.xpos + "!!!!!");
    }

    void printPos() {
        println("x: "+xpos);
        println("y: "+ypos);
    }
}

Test t = new Test();
void setup() {
    t.printPos();
    exit();
}

GoToLoop, i have tested it ....it works but keep in mind that are tricky when extending classes, you usually use them to share code with all your constructors.
try this

1. class Parent {
2.   float xpos=5;
3.   float ypos=8;
4.  
5.   Parent(){
6.     println("CALLED ME?");
7.   }
8. }
9. class Test extends Parent {
10.   // why can't I do it this way?
11.  {
12.     xpos = 100;  //  <---   force an early initialization
13.     //          even before constructor!!!
14.   }
15.   {println("second Instance initialization block\n");}
16.   Test() {
17.     println("xpos is already = " + xpos + " before getting here!!!");
18.     println("even parent's xpos is set -> " + super.xpos + "!!!!!");
19.   }
20.  
21.   {print ("first instance initialization block block\n");}
22.   void printPos() {
23.     println("x: "+xpos);
24.     println("y: "+ypos);
25.   }
26. }
27. Test t = new Test();
28. void setup() {
29.   t.printPos();
30.   exit();
31. }

they actually run after you subclass has implicitly called you super constructor and in the order you have them in the class..

another thing is that in processing these classes are actually inner classes that is why you  cannot declare these initialization blocks static unless they are outside you class definition


breflabb here is an introduction by shiffman http://natureofcode.com/book/chapter-4-particle-systems/

The curly braces section in a class without declaration before (not enclosing a method's body) is called a static initialization section.
It is run even before the constructor, after the initializations made in the field declarations.
One interest of such section is that you can do things not allowed in a declaration section, like having local variables or calling methods (eg. ArrayList's add).

This is rarely used, and I saw it only in top-level classes, where it can be used only to do complex initialization of static variables: ie. it is ran only once, probably on the first instantiation of the class.
I admit I am not too sure of the exact behavior in nested classes, like the ones declared in .pde files.

...
I checked, it looks like it is just ran before the constructor, on each instance.

i see, had no idea that there where some thing like that , i have learned a ton ! :D

@Dimiro wow that is a nice link, with a lot of interesting topics !

thank you all, my Xmass have arived earlier then i expected :D

I updated my answer with some clarifications...