This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
Though I understand the mechanics of using an interface, I'm not fully appreciating its usefulness. I realize they're very important, but why? After all, I'm the one who has to provide all the code to perform the function I require, so how is it benefiting me?
Originally posted by Dan Bromberg: Though I understand the mechanics of using an interface, I'm not fully appreciating its usefulness. I realize they're very important, but why? After all, I'm the one who has to provide all the code to perform the function I require, so how is it benefiting me?
Even though you have to create the code for the interface implementation methods to work, the code calling your object doesn't have to know how it works, doesn't have to know even what class it is working on, just that the object implements that interface, and that it will work as expected. This is tremendously liberating. Have a look at an article on one of the software design patterns such as the observer pattern (you use this for instance anytime you code using Swing) and you'll see the power and beauty if this idea.
I'd look at it from a different angle. Interfaces come in handy when you are working with other poeple, teams, or even companies. I write an interface. I write my code to take objects that implement that interface. I then go to the person/team/vendor and say "make your object implement this interface".
When they do, they can then send me objects that i've never dreamed existed, and my code works.
a year from now, when we decide to go with a new vendor, I can sit on the beach drinking Mai-tais after handing them my interface. THEY implement it, and I get a nice tan. When they're done, I know my code already works, so life is GOOD!!!
There are only two hard things in computer science: cache invalidation, naming things, and off-by-one errors
interface force anybody who implement it to overide the method. And also there is common also to define static final Object in the interface. It make the program to be as modular as possible by use Interface.
There are a number of situations in software engineering when IT IS IMPORTANT FOR DISPARATE GROUPS OF PROGRAMMERS TO AGREE TO A "CONTRACT" that spells out how their software interacts. Each group should be able to write their code without any knowledge of how the other group's code is written. Generally speaking, INTERFACES ARE SUCH CONTRACTS.