Square class "implements" the Polygon interface ("The Perimeter of Rectangle is: " +2*(length + breadth)) The body of getPerimeter() is provided here ("The Area of Rectangle is: " +length*breadth) The body of getArea() is provided here The body of getNumberOfSides() is provided here ("The name of the Polygon is: Rectangle") The body of getName() is provided here Rectangle class "implements" the Polygon interface declaring interface methods(without a method body) Public static final int side = 5,length = 4,breadth = 8 The implements keyword appears in the class declaration after the extends portion of the declaration.Ĭode to understand Interfaces in Java: package In order to implement an interface, a class uses the implements keyword. Unless a class is declared as abstract, it should perform all the behaviors of the interface. This means that the class agrees to perform the specific behaviors of the interface. It is illustrated in the image below:Ī class implementing an interface can be thought of as the class assigning a contract. It also adds public, static and final keywords before the data members. Note: The Java compiler automatically adds the public and abstract keywords before the methods of an interface. Hold On! It’s the right time to take a deep dive into the concept of Inheritance in Java with some real-life examples. We also use them for gaining loose coupling.We also use them to support the functionality of multiple inheritances in Java.Use interfaces to achieve data abstraction.In other words, interfaces can declare only constants, not instance variables. All variables defined in an interface are public, static, and final.Each method in an interface is implicitly public.Each method of an interface is also implicitly abstract, so we need not use the abstract keyword while declaring methods inside an interface.While declaring an interface, you do not need to use the keyword abstract. Filename : Animal.java interface AnimalĪn Interface has the following properties − Any number of abstract method declarations Here is a syntax to declare an interface: interface interface-nameįollowing is an example of an interface: //Filename: NameOfInterface.java
To declare an interface, the interface keyword is used. An interface cannot implement any class or another interface.An interface can not be extended or inherited by a class it is implemented by a class.It can only contain the fields that are declared as both static and final. An interface cannot contain instance fields.An interface does not contain any constructors, but a class can.All the methods in an interface should be declared as abstract.Unlike a class, you cannot instantiate or create an object of an interface.Since Java 9, we can also include private methods in an interface.ĭifferences between Interface and Class in Java.Since Java 8, we can have static and default methods in an interface.We can implement more than one interface in our class.An interface can inherit or extend multiple interfaces.Java Interface also represents the IS-A relationship of inheritance between two classes.The word abstract means these methods have no method body, only method signature. All methods of an interface are implicitly public and abstract. We can implement multiple Java Interfaces by a Java class.An interface provides a set of specifications that other classes must implement.An interface in Java is a mechanism which we mainly use to achieve abstraction and multiple inheritances in Java.These abstract methods are implemented by classes before accessing them.The methods in interfaces do not contain any body. It also has capabilities to perform a function.An interface in Java basically has a set of methods that class may or may not apply. An interface provides specifications of what a class should do or not and how it should do.Interfaces are one of the core concepts of Java programming which are majorly used in Java design patterns.The class that implements the interface should be abstract, otherwise, we need to define all the methods of the interface in the class.īefore moving ahead in this article it is recommended for you to take a quick revision on Classes in Java with Techvidvan. There can be only abstract methods in an interface, that is there is no method body inside these abstract methods.
It is much similar to the Java class but the only difference is that it has abstract methods and static constants. In Java, an interface is a blueprint or template of a class. Public interface AutoCloseable Īn Array array could be used e.g.Keeping you updated with latest technology trends, Join TechVidvan on Telegram Interfaces in Java
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