Question

There is base class A which has a method to load a data source.
Various classes are derived from A including derived class B.

Now I need to have a static member variable in class B e.g. mStaticOfB that is instantiated only once for ALL instances of class B to use.

The caveat here is that to instantiate the static mStaticOfB I need to use the data source inherited by base class A.But I need an instance of an object to get that and I don’t have it at that point.

How can I get arround this problem? Is there a good/standard way to handle this?The only idea that I came up (and trying not to use) is to make
class B a singleton.

Answer 1

What Nishant said, except threadsafe:

private static FieldType mStaticOfB;
...
public B(..) {
   super();
   synchronized(B.class) {
      if (mStaticOfB == null) {
         //code to set mStaticOfB
      }
   }
}