An interface is similar to a class but it is used to define the specification of a behavior. It is a collection of operations specifying the externally visible behavior of a class. It has no implementation of its own.
An interface can be created in the following diagrams:
An interface includes the signatures of the operations. It specifies only a limited part of the behavior of a class. A class can implement one or more interfaces.
A class must implement all the operations in an interface to realize the interface. The following example shows an interface (Designated) realized by a class (Employee).
