I am new to design
patterns and am not able to understand the Observable pattern of java.util pattern.
In the first chapter I learned the second design principle saying "Program to interface not to implementation". That being said when I moved to the second design pattern the Observer Pattern chapter, I came across the dark side of java.util.Observable where the picture talks about violating the OO design principle of programming to interfaces and not implementation. I didnot get this point, can any one well-versed in this concept throw some light on it.
Suppose I have an class BASE and a subclass EXTENDED which extends BASE, isn't the whole point of the design principle
Program to interface not to implementation
mean
So whenever I use an Observable object I am going to use something like this
Regards
Kumaravel J