Decorator Pattern

[Maan Suraj]

I was going through decorator pattern from Head First. On one of the pages,it says that

" When i inherit behaviour by subclassing,that behaviour is set statically at compile time"

I am not getting what does "statically at compile time means in this context".

[ramesh maredu]

I read it long back,if I am correct, the book is comparing between inheritance and composition.

When you extend a class and make a subclass then you get the behavior of super class and the behavior is static (you can not change the behavior at runtime). But if you compose then the behavior you get with composed reference could be dynamic.

class A{ 
   void doSomethig()
}

class B extends A{
  //the behavior you get here is of class A and there is no way to change it dynamically
}

class B{
A a;
//here the behavior you get with a could be dynamic as you can have sever implementations (subclasses) of A, and any implementation could go into a reference variable.
}