Question

“Can anyone explain me execution flow for the following java code ??”
Sorry for my misleading statement… my question is …

Main b = new Main();

control goes to the A class constructer, then control directly goes to the overriden method of class Main

public void PrintFields() {
    System.out.println("x = "+x+" y = "+y);
}

Why compiler doesn’t give error because x and y is not created..!! i am confused in this only.

When will x and y created in memory and when its initialization takes place ?? is the x and y created when control reaches to following statements in Main class ?

int x = 1;
int y;

Code:

class A
{
    public A() {
        PrintFields();
    }
    public void PrintFields() {}
}
class Main extends A
{
    int x = 1;
    int y;
    public Main() {
        y = -1;
        PrintFields();
    }
    public void PrintFields() {
        System.out.println("x = "+x+" y = "+y);
    }
}
class Test
{
    public static void main(String[] args) {
        Main b = new Main();
    }
}

Output:

run:
x = 0 y = 0 //why 0 0 ?
x = 1 y = -1 // why 1 -1 ?
BUILD SUCCESSFUL (total time: 0 seconds)

Thank you.

Answer 1

Main b = new Main();

control goes to the A class constructer, then calls the overriden method of class Main

public void PrintFields() {
    System.out.println("x = "+x+" y = "+y);
}

At this time x and y have their default values

so x=0, y=0

Now control comes to

int x = 1;
int y;
public Main() {
    y = -1;
    PrintFields();
}

and then

public void PrintFields() {
    System.out.println("x = "+x+" y = "+y);
}

at this time x =1 and y=-1

so output is

x=1, y=-1