While going through some lecture video on interface. I noticed
If we don't know about implementation, just requirement specification then go for interface.
What can be the scenario? Though I've used interface in many cases, but didn't gwt the essence of interface, as stated.
If we don't know about [the] implementation, just the requirement specification, then go for interface.
What that means is that you can sketch out an architecture by designing and writing the interfaces first, and defer writing the implementations that satisfy those interfaces to a later time.
Let's say you're one of the designers of the Java development environment. You want to provide a sort function for your collections. But you don't know how to sort custom types (i.e. user-defined classes) because you don't know how to determine whether one object of a given class is greater than another. You can't write an implementation for that comparison, because you don't know how to do that for any given class that someone may write.
So you provide an interface called Comparable. It defines a method
int compare<T>(T other)
that takes as a parameter an "other" object of the specified type, and returns a number that tells Java whether the other object is equal, greater than or less than this object. Now you can let people derive their class from your interface and write a Compare method implementation. Your sort function now understands how to sort these objects because it understands Comparable and can call their Compare method to compare two instances of their objects.
The essence of an Interface is a contract.
I don't care how the result is achieved, just that
If I do care about the implementation, then I would use a base class or abstract class, allowing me to specify some of the code to be run by all child classes.
