static reference var & singleton

[Mark Henryson]

Hi all,

I have one doubt in static.

I know the instance variables are one per object.
And the Static Variables are one per class.

I have used like below:
int i = 10; //Instance variable
static int i = 10; // Static Variable.

I comw across like this:
static Dog d = new Dog();

Pls explain the above line and its importance. And also I come across this cdoings in Singleton class and whether inheritance is possible in the singleton class. Since we are marking construtor as private. pls explain that too

[Mark Henryson]

If possible provide me some sample codings!!

Thanks!!

[Mark Henryson]

I tried some codings. pls go thru it.

class ex
{
   int a,b; 
   static int c;
   
   public static void main(String args[])
   {
     ex e1 = new ex();
     ex e2 = new ex();
   }
}

Correct me,if i am wrong: In the above pgm.

           ______ a, b  
  _______ /  
  | e1  |/
  ------- \
           \_______ c
  _______  /
  | e2  | /
  ------- \
           \_______ a,b
 
e1 will have its own "a" and "b";
e2 will have its own "a" and "b";
Since "c" is static it will shared by both e1 and e2.

If possible like above what will be the result for:
static ex e3 = new ex();

[Stan James]

You're on the right track here. A third instance will get its own copy of a,b and share c again.

If your class will modify c you have a great reason to read up on threads and synchronize.