The purpose of the interface is to separate a class’s interface from its implementation. Interface just defines what a class must do without saying anything about the implementation. Interfaces define only method signatures and they do not have any instance variables. Interfaces are very good tool for designing as you can just define signatures of public methods without going into
implementation details, which are left for the person implementing the interface.
Using the keyword interface, you can fully abstract a class‘s interface from its implementation. That is, using interface, you can specify what a class must do, but not how it does it.
Interfaces are syntactically similar to classes, but they lack instance variables, and their methods are declared without any body. In practice, this means that you can define interfaces, which do not make assumptions about how they are implemented. Once it is defined, any number of classes can implement an interface. Also, one class can implement any number of interfaces.
To implement an interface, a class must create the complete set of methods defined by the interface. However, each class is free to determine the details of its own implementation. By providing the interface keyword, Java allows you to fully utilize the “one interface, multiple methods” aspect of polymorphism.
Interfaces are designed to support dynamic method resolution at run time. They disconnect the definition of a method or set of methods from the inheritance hierarchy. Since interfaces are in a different hierarchy from classes, it is possible for classes that are unrelated in terms of class hierarchy to implement the same interface. This is where the real power of interfaces is realized.
Note: Interfaces add most of the functionality that is required for many applications, which would normally resort to using multiple inheritance in a language such as C++.
implementation details, which are left for the person implementing the interface.
Using the keyword interface, you can fully abstract a class‘s interface from its implementation. That is, using interface, you can specify what a class must do, but not how it does it.
Interfaces are syntactically similar to classes, but they lack instance variables, and their methods are declared without any body. In practice, this means that you can define interfaces, which do not make assumptions about how they are implemented. Once it is defined, any number of classes can implement an interface. Also, one class can implement any number of interfaces.
To implement an interface, a class must create the complete set of methods defined by the interface. However, each class is free to determine the details of its own implementation. By providing the interface keyword, Java allows you to fully utilize the “one interface, multiple methods” aspect of polymorphism.
Interfaces are designed to support dynamic method resolution at run time. They disconnect the definition of a method or set of methods from the inheritance hierarchy. Since interfaces are in a different hierarchy from classes, it is possible for classes that are unrelated in terms of class hierarchy to implement the same interface. This is where the real power of interfaces is realized.
Note: Interfaces add most of the functionality that is required for many applications, which would normally resort to using multiple inheritance in a language such as C++.
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