SCJA Question About Ancestor and Sub Classes

[Oscar Hansen]

I am reading SCJA book by Cameron McKenzie and on page 166, I did not understand the answer to a question. Can someone explain me:

Sub classes:
- Should not be used as a method parameters when an ancestor class will suffice.

Thanks in advance!

[Cameron Wallace McKenzie]

The basic idea is that you always want to use the most general component whenever possible.

So, if I have a method, and all it does is print out the toString() method, I shouldn't force the argument to be a String, when I could just make the argument an Object. After all, every instance of an Object has a toString() method.

The more general, or abstract an argument is, the more flexible the method becomes. It makes your code more flexible and pluggable. That's the general idea.