Defining an interface An interface is a named set of behaviors and/or constant data elements for which an implementer must provide code. An interface specifies what behavior the implementation provides, but not how it is accomplished. Defining an interface is straightforward public interface interfaceName returnType methodName argumentList An interface declaration looks like a class declaration, except that you use the interface keyword. You can name the interface anything you want to subject to language rules, but by convention interface names look like class names. Methods defined in an interface have no method body. The implementer of the interface is responsible for providing the method body just as with abstract methods.