Static keyword?

HI there,

Yes, a static variable or method can be called without instantiating the class. Also, a static variable is shared across all instances of that class - it only has memory allocated once.

So, you could define a static member variable that is initialised to zero:

static int numberOfInstances = 0;

Then, inside the constructor, it can be incremented:

class MyClass{

static int numberOfInstances = 0;

  public MyClass(){
    // do the constructor stuff
    numberOfInstances++;
  }
}

Now, we can access that member variable (which is the same member variable for all instances of MyClass which will tell us how many objects of MyClass exist.

The key thing is memory efficiency. A static variable only gets allocated one slot of memory irrespective how many instances of the class exist, they all point to that static variable.

I hope that makes sense!

Steve.