wrapper's initial value

[Michelle Chang]

Here is part of code somewhere in KB's book.

  
public class Beyond extends Infinity {
static Integer i;
public static void main(String[] args) {}
}

Just a small question here. Does static variable get its initial value when the class is loaded? If that is the case, my next question is that is i's initial value in line 3 null because it's a wrapper class?
Thanks.

[Larry Olson]

Yes, all static variables get initialized when a class is loaded. Wrapper variables are initialized to null, since it is a non-primitive type.

I would strongly recommend that you install jdk on your computer/laptop or whereever and start typing this code, compile it and execute it for yourself to see the results - in this case confirm that the Integer variable indeed gets a null value. Try to do a demo code for every concept you learn and execute it. You will enjoy it and believe me, you will not forgot the concept easily.

[Prasad Kharkar]

and yes, I would also like to tell you that static variables are completely related to class and they have nothing to do with objects
they are initialized when the class first loads

and about the instance variables, they are given the default values when the object is created and it calls the respective constructor

[Prithvi Sehgal]

Please quote the source for the above mentioned source code.

Regards,

[Afzal Rehman]

static variable initialized when class loads

  
public class Test{
	 static int i;
	 public static void main(String[] args){
	
	System.out.println(i);
		
	
	}
}
  

Output will be 0.

but if you try to print i as an instance variables initialized by default values when instance created
see the example.

 
 public class Test{
	 int i;
	 
	 public Test(){ }
	 
	 public static void main(String[] args){
	 	 
		System.out.println(new Test().i);
		
	}
}  

it will produce Output 0.

but look at this example ...

 

public class Test{

	 public Test(){ }
	 
	 public static void main(String[] args){
		int i;
	 	 
		System.out.println(i);
		
	
	}
}
 

This will produce an Compiler error int i is being not initialized. so keep concentration when you are using variables in a methods
those being initialized or not...