Simple newbie codes..

[kampong]

Hi
i taking some course now on OO
can someone explain these codes to me?
i cant seems to understand

class Root {
public Root() {System.out.println("Root Object");}
public Root(String s) {System.out.println("Root " + s);}
public void grow() {System.out.println("Root grows!");}
}
class Tree extends Root {
public Tree() {System.out.println ("Tree Object");}
public Tree(String s) {System.out.println("Tree " + s);}
public void grow() {
super.grow();
System.out.println("Tree grows!");
}
}
class Leaf extends Tree {
public Leaf() {System.out.println( "Leaf Object");}
public Leaf(String s) {System.out.println("Leaf " + s);}
}

public class Forest {
public static void main (String[] args) {
new Leaf( "FOREST" );
Root root1 = new Tree(),
root2 = new Leaf();
root1.grow();
root2.grow();
}
}


results:
Root Object
Tree Object
Leaf FOREST
Root Object
Tree Object
Root Object
Tree Object
Leaf Object
Root grows!
Tree grows!
Root grows!
Tree grows!


but how come??

[Fubarable]

which part confuses you?

One key thing to know is that whenever you call a class's constructor, it first calls the constructor of the parent's class all the way up the the parent tree (as you're seeing).

[Fubarable]

To the original poster, cross-posting can frustrate anyone who tries to help you only to find out later that the same answer was given hours ago in a cross-posted thread. No one likes wasting their time, especially a volunteer. The polite thing to do would be to not do this, but if you feel that you absolutely must, to at least provide links in both cross-posts to each other.

Keep this up, and you will be placed on the do-not-help list of many of the volunteers here and elsewhere.

[kampong]

i cant figure out why the order is like tat..
coz i am quite new to java too..
which one is the parent class?
which one is the parent tree like u said?

[kampong]

oh!
sorruyy
really new to here and i dont know the rules well
:X
will not repeat cross posting again

[Fubarable]

class Root
{

}

class Tree extends Root
{

}

Please take an educated guess: which is the parent class and which is the child class?

[Fubarable]

Also, have a look at your text book and here for info on basic OOP concepts: Lesson: Object-Oriented Programming Concepts (The Java™ Tutorials > Learning the Java Language)

[kampong]

class Root
{

}

class Tree extends Root
{

}

Please take an educated guess: which is the parent class and which is the child class?

Root is the parent class
which line is "call class's constructor"?

[Fubarable]

My example has no constructors but is just to illustrate an inheritance hierarchy. Are you familiar with what a constructor is and how it is called? If not, then please study your text and the link I provided. You've much to learn but with diligent study you'll get there!

[kampong]

ok. will read up first.
tks for the link :)
any doubts will ask u again
:D