11/11/2023 0 Comments Java interface design tutorialFor example, when we start our car, we just plug in the key and start the car without worrying about the nitty-gritty details of what happens underneath when the car starts. For abstraction: Interfaces help to achieve security, hide certain details, and only show the relevant and necessary information.To solve this, we can use a Java interface to give child classes the freedom to extend whatever parent class they wish (and implement our interface) rather than forcing them to extend a specific base class to use our functionality. Multiple inheritances: In Java, we cannot extend multiple classes because of the famous Diamond problem (explained later in this article).We can take any object that implements the Car interface as a parameter and call the start method on it. This is essentially an interface- a checklist! It is a set of methods you want a class to implement to accomplish a certain task. You leave them a checklist of things to be done to bake a cake. Intuition behind Using an Interface in JavaĪssume you are the head baker of a reputed baking chain, and you want to give instructions to the other bakers under you on the steps they need to follow to bake a cake. These methods are public and abstract by default(you don’t have to explicitly use the “ abstract” keyword), and any class implementing your interface will need to provide implementations of those methods. What is an Interface in Java?Īn interface is a set of abstract methods you would want your class to implement. Interfaces are used to achieve abstraction and implement multiple inheritance.Īs complex as it may be to wrap your head around this concept, this article will unravel the world of Interfaces in Java for you with practical examples. It is the blueprint of a class and contains static constants and abstract methods. 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.Interfaces in Java are a set of abstract and public methods we want our classes to implement. 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. Method bodies exist only for default methods and static methods. 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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