![]() For example, the MouseListener interface in the package extended, which is defined as − ExampleĪn interface with no methods in it is referred to as a tagging interface. ![]() The most common use of extending interfaces occurs when the parent interface does not contain any methods. HockeyDemo hockeyDemo = new HockeyDemo() Public class MammalInt implements Animal The implements keyword appears in the class declaration following the extends portion of the declaration. If a class does not perform all the behaviors of the interface, the class must declare itself as abstract.Ī class uses the implements keyword to implement an interface. When a class implements an interface, you can think of the class as signing a contract, agreeing to perform the specific behaviors of the interface. Methods in an interface are implicitly public. You do not need to use the abstract keyword while declaring an interface.Įach method in an interface is also implicitly abstract, so the abstract keyword is not needed. Interfaces have the following properties −Īn interface is implicitly abstract. Any number of abstract method declarations\ Here is a simple example to declare an interface − Exampleįollowing is an example of an interface − The interface keyword is used to declare an interface. The only fields that can appear in an interface must be declared both static and final.Īn interface is not extended by a class it is implemented by a class.Īn interface can extend multiple interfaces. However, an interface is different from a class in several ways, including −Īn interface does not contain any constructors.Īll of the methods in an interface are abstract.Īn interface cannot contain instance fields. Interfaces appear in packages, and their corresponding bytecode file must be in a directory structure that matches the package name. The byte code of an interface appears in a. java extension, with the name of the interface matching the name of the file. Unless the class that implements the interface is abstract, all the methods of the interface need to be defined in the class.Īn interface is similar to a class in the following ways −Īn interface can contain any number of methods.Īn interface is written in a file with a. And an interface contains behaviors that a class implements. But a class describes the attributes and behaviors of an object. Writing an interface is similar to writing a class. Refer to this question for when to use each of them: Interface vs Abstract Class (general OO) Example to understand things. With java 8 release, interface can have default methods in interface, which provides implementation in interface itself. Method bodies exist only for default methods and static methods. The class implementing the interface 'has a' capability. A class implements an interface, thereby inheriting the abstract methods of the interface.Īlong with abstract methods, an interface may also contain constants, default methods, static methods, and nested types. An interface is a reference type in Java.
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