Interfaces

• An Interface in Java programming language is defined as an abstract type used to specify the behavior of a class.
• An interface in Java is a blueprint of a class.
• A Java interface contains static constants and abstract methods.
• Like a class, an interface can have methods and variables, but the methods declared in an interface are by default abstract (only method signature, no body).
• Interfaces specify what a class must do and not how. It is the blueprint of the class.
• An Interface is about capabilities like a Player may be an interface and any class implementing Player must be able to (or must implement) move(). So it specifies a set of methods that the class has to implement.
• If a class implements an interface and does not provide method bodies for all functions specified in the interface, then the class must be declared abstract.
• Interface is used to achieve total abstraction.
• Since java does not support multiple inheritances in the case of class, by using an interface it can achieve multiple inheritances.
• Interface is also used to achieve loose coupling.
• Interfaces are used to implement abstraction.