about constructors

[Parameswaran Thangavel]

hi



1) i know that static codes are executed when the class is loaded.
when will the instance or member variables get initialized is it b4 constructor get invoked or at the end of the constructor.

2) and also is possible to use the instance variable before creating instance i.e at the middle of constructor if it so how and why?

3) kindly go throug the code along the comments.

class Phone {
static String device = "Phone.device";
void showDevice() {
System.out.println("Phone.showDevice," +

device + " ");
}
Phone() {
System.out.println("hai" + Phone.device);//working fine (1)
//System.out.println("hai" +Mobile.device);--->Throwing the error non-static cannot be referenced //from static context is that mean constructor is static
System.out.println("hai" + this.device);//the constructor is invoked from the Mobile then the o/p //should be Mobile.device but not so why??
showDevice();
}
}

class Mobile extends Phone {
String device = "Mobile.device";
void showDevice() {
System.out.println("Mobile.showDevice," + device + " ");
}
Mobile() {
//System.out.println("hai" + Mobile.device);//same error explained above.if (1)is working fine why //not this
System.out.println("hai" + Phone.device);//working fine.
System.out.println("hai" + this.device);
showDevice();
}
public static void main(String[] args) {
Mobile n = new Mobile();
n.showDevice();
}
}




i am sorry to post lot of questions but it is just to make ourself comfortable with the topics.

so please do reply to all the questions.

[Jeff Jetton]

i am sorry to post lot of questions but it is just to make ourself comfortable with the topics.

so please do reply to all the questions.

I'd love to help, but I'm having a hard time reading your code the way it is currently formatted.

If you would edit your post and use "code" tags around your code, that will preserve the indentations. Code that is properly indented is much easier to read!

- Jeff

[vinuharan haran]

hi,
1).First the object is allocated memory.To be clear,the instance variables are given default values.The instance variables are then intialised before the constructor call.
2)so it is possible to use the instance variables in the constructor.
In your code the String variable device in Mobile is not static.So u cannot access it with classname.Thats why the compiler complains.The constructor cannot be static.
Another thing...Static variable can hide the instance variable.
A) If the variable device in Mobile is declared static
Static variable device in Mobile hides the static variable device in Phone.
this.device in Phone class constructor refers Phone.device.It refers the variable in closer context.
this.device in Mobile class constructor refers Mobile.device.The same explanation holds good.i.e it refers the variabe in closer context.

B) If the device in Mobile is instance variable then this.device in phone constructor has the value null.This is because the variable is not initialised.so it has the default value.
Hope this helps...