SARAL perfect article, agreed that is most hot question in java world.!! :). VisaPaymentGateway gateway = (VisaPaymentGateway) getComponent("VisaPaymentGateway") //bad, could have broken PaymentGateway gateway = (PaymentGateway) getComponent("VisaPaymentGateway") //Ok Public class VisaPaymentGateway implements PaymentGateway
JAVA INTERFACE RULES CODE
Never type cast object into implementation, instead if you need to, cast into interface or abstract class as shown in following code : Code written using interface are much more flexible than otherwise.
So use interface on declaring member variable, local variable, method parameters, return type or anywhere you need a Type. Programmers was type casting into specific class, even if they are calling public methods of interface, this code was fragile and broke once I have added another implementation of interface. Recently I had to refactor lot of code, which was dependent on class which implements interface than the interface itself. One should always use interface for declaring Types and always code against interface than any particular implementation. Please le t me know, if my answer is correct? I said, concrete class because we definitely wants to provide default implementation of State and let's specific state only overrides methods, which make sense on those state. Hello guys, in state design pattern, should we use an abstract class or interface for modelling State abstraction? this was asked to me in a recent java interview. I don't like empty methods and no functional code, which is the case with Java interface. My reason of using Abstract class is simple, avoid using interfaces until Java 8 comes with default method implementation. Interface in my opinion can represent highest level of abstraction, and abstract class may be with slightly lower than, given they have some sort o implementation, which as you said good for low levels of system architecture. Javin puzzle asked in programming Acargil, I sort of agree with you. my point of view, abstract classes are best fit in low levels of system architecture: persistency, network, web, ui to keep common things under control and reduce redundancy. Well detailed notes about legendary diferrence, thx. They always looks similar to me, but I love the way you explain things, If you don't mind, can you take an example and walk though us of using Interface over abstract class, and another example in which abstract class is more suitable than interface? Anyway, learn so many things on object-oriented programming from you, Thank you. I have faced this question couple of times on interviews, but not able to give proper example, when it comes to choosing interface over abstract class or vice-versa. More discussion on their restrictions should be attached. Think the difference between abstract class and interface may be given point wise. Subclassing makes testing and reasoning about your code more difficult. When should you use abstract classes and interfaces? Always.
JAVA INTERFACE RULES SOFTWARE
It's best to get this kind of knowledge as part of your work but even if you don't get there, you can supplement them by joining a comprehensive course like these Java design Pattern courses and doing some object-oriented software design exercises. In order to best understand this topic, you need to work out some scenarios, examples, etc.
Questions like when to use abstract class and interface fall under the same category. The repercussion of design decisions is best known during the maintenance phase, the good design allows seamless evolution while maintaining a fragile design is a nightmare.Īs I have said previously, sometimes object-oriented design interview questionsalso helps to understand a topic better, but only if you are willing to do some research and not just mugging the answer. Many programmers fumbles here, which is natural because most of them haven't gone through the real system design process and haven’t seen the impact of choosing one over another. Things start getting difficult when the interviewer asks about when to use abstract class and interface in Java, which is mostly based upon a solid understanding of popular OOPS concepts like Polymorphism, Encapsulation, Abstraction, Inheritance, and Composition. The question usually starts with a difference between abstract class and interface in Java, which is rather easy to answer, especially if you are familiar with the syntax of the Java interface and abstract class.
In this article, we will mostly talk in the context of the Java programming language, but it equally applies to other languages as well. When to use interface and abstract class is one of the most popular object-oriented design questions and is almost always asked in Java, C#, and C++ interviews.
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