Why do most system architects insist on first programming to an interface?

Question

Almost every Java book I read talks about using the interface as a way to share state and behaviour between objects that when first \"constructed\" did not seem to share a r

Answer 1

Its all about designing before coding.

If you dont know all the relationships between two objects after you have specified the interface then you have done a poor job of defining the interface -- which is relatively easy to fix.

If you had dived straight into coding and realised half way through you are missing something its a lot harder to fix.