Related to the idea of Inheritance is a concept supported by many…object-oriented languages which usually referred to as an interface.…Now this can get a little puzzling because the word Interface is heavily used in…computing and has several different meanings.…But the term here does not mean user interface.…What we are talking about here in this discussion is something that's…actually created very similar to a class but with no actual functionality,…no actual code, no behavior.…It's really just a list of method signatures.…

In Java an interface would be written something like this, just the word…interface instead of class.…Give it a name. I am calling it Printable, and then two method signatures…with absolutely no functionality, you're not allowed to put functionality…inside an interface.…Now you might think, well, what's the point of this?…Well, the idea is that if we create a new class and then choose to use an…interface--and the term we use is implementing an interface--it's like signing a contract.…