This website or its third-party tools use cookies, which are necessary to its functioning and required to achieve the purposes illustrated in the cookie policy. The most important of all is that the application becomes secured as the implementation after making abstract is hidden from the outside world, thus maintaining the security aspects as well. The client-side perspective of expecting a set of services to be delivered to the end-user is known as interface, and from the perspective of service providers, the set of services being offered is known as the interface. The abstract class consists of both abstract class as well as normal methods or non-abstract classes, but the case is not the same with the interface. Many times, people get confused between abstract class and interface, but they are different. Start Your Free Software Development Course, Web development, programming languages, Software testing & others. Then there is one more essential aspect to be followed with interface declaration and implementation. But a class can implement multiple interfaces. You may also look at the following articles to learn more , Java Training (40 Courses, 29 Projects, 4 Quizzes). This is a guide to Interface in Java. By signing up, you agree to our Terms of Use and Privacy Policy. A subclass can extend only one abstract class but it can implement multiple interfaces. It maintains IS-A-Relationship, which also helps make the inheritance and extend between classes possible, thus providing visibility. Abstract classes can have constructors but interfaces cant have constructors. However, the main aim of the interface in java is to achieve 100% abstraction by hiding actual implementation to the user and thus making applications a bit user-friendly. Following are the examples of implementing an interface in java with different scenarios: The above output tries to prove the point that the interface must be implemented by another class using the implements keyword rather than using the extends keyword. The Interface is a medium to interact between user and system devices. Abstract classes can have methods with implementation whereas interface provides absolute abstraction and cant have any method implementations. Here we discuss the introduction and how does the interface work in java, along with examples to implement an interface.

ALL RIGHTS RESERVED. If we see a bigger picture of java, then the interface plays a pivotal role in how any service requirement specification is considered an interface. Part of JournalDev IT Services Private Limited, Difference between Abstract Class and Interface in Java, https://www.journaldev.com/1601/what-is-interface-in-java-example-tutorial. As it is most often defined as IS-A-Relationship, it is used to achieve loose coupling. If an interface is getting implemented, it must declare the interface as public; otherwise, it will throw an error saying compile-time error. It has really helped the main framework of applications make them secured and came a lot to become user-friendly. By closing this banner, scrolling this page, clicking a link or continuing to browse otherwise, you agree to our Privacy Policy, Explore 1000+ varieties of Mock tests View more, Special Offer - Java Training (40 Courses, 29 Projects, 4 Quizzes) Learn More, Java Training (41 Courses, 29 Projects, 4 Quizzes), 41 Online Courses | 29 Hands-on Projects | 305+ Hours | Verifiable Certificate of Completion | Lifetime Access | 4 Quizzes with Solutions, JavaScript Training Program (39 Courses, 23 Projects, 4 Quizzes), jQuery Training (8 Courses, 5 Projects), Java Interview Question on Multithreading, Multithreading Interview Questions in Java, Software Development Course - All in One Bundle. The first need is to make the application very user-friendly, which can be done by making two different systems communicate via each other smoothly via interface [i.e., making a java application talk with the mainframe systems interface. THE CERTIFICATION NAMES ARE THE TRADEMARKS OF THEIR RESPECTIVE OWNERS. By declaring interface keyword: We can declare an interface by using the interface keyword and implement it by using the implement keyword. Therefore, if a class implements an interface mandatorily, we should provide an implementation for every method of that interface; otherwise, that class must be declared as abstract. Abstract classes can extend other class and implement interfaces but interface can only extend other interfaces. Also coding in terms of interfaces is one of the best practices for coding in java. Therefore, it basically comprises of static, abstract, and final methods. Also if subclasses dont need to implement a particular method, they can avoid providing the implementation but in case of interface, the subclass will have to provide the implementation for all the methods even though its of no use and implementation is just empty block. Abstract class have all the features of a normal java class except that we cant instantiate it. Applications will be enhanced and optimized as well as simplified as its internal implementation is not the concern of the end-user. Note that from Java 8 onwards, we can create default and static methods in interface that contains the method implementations.

We can use. Similarly, in Java, Interface also plays the same role; it is considered as an interactive medium between the system and the end-user. Interfaces are used to define contract for the subclasses whereas abstract class also define contract but it can provide other methods implementations for subclasses to use. The interface gives its 100% and can achieve full abstraction, but this is not the case with the abstract class, which provides partial abstraction only. 2022 - EDUCBA. One interface can extend another interface also once a class can implement an interface. So most of the times Interfaces are a good choice for providing the base for class hierarchy and contract. Abstract classes methods can have access modifiers as public, private, protected, static but interface methods are implicitly public and abstract, we cant use any other access modifiers with interface methods. An interface contains only an abstract method, but java 8 can accommodate both default and static methods also which is like add-on. If there are a lot of methods in the contract, then abstract class is more useful because we can provide a default implementation for some of the methods that are common for all the subclasses. For example, in our real life, if we consider the interface to be given as an example is the air condition, bike, ATM machine, etc. If our base contract keeps on changing then interfaces can cause issues because we cant declare additional methods to the interface without changing all the implementation classes, with the abstract class we can provide the default implementation and only change the implementation classes that are actually going to use the new methods. There are three main reasons why do we need it. The nested interface is yet another type of interface that we can suggest by its name as an interface within an interface and comes as a part of nested classes as well. Therefore, as mentioned earlier with a real-life example, an interface in java is nothing but a contract between the client-side and service providers. Implementation of an interface in java is performed by using implements keywords. Java doesnt support multiple class level inheritance, so every class can extend only one superclass.