Implicit Interfaces

There are many kinds of "interfaces."

There are interfaces the Java language construct - these let you specify methods that different classes will share and write code that will work against anything which implements that interface.

But there are also "interfaces" that you encounter in the real world. The classic example is an automobile. Once you understand the "interface" of a steering wheel, brake pedal, and gas pedal you can drive most any car.

Then back within Java there are things which form "an interface" which may or may not use the interface keyword. The static methods available on a class, the constructors that are public, the set of classes that come with a library, etc.

I think a more general concept "the implicit interface." Everything you can observe about a thing forms its "implicit interface."¹