If anyone has any other idea, than please share.ġ) create one new Abstract class which implements original interface. I know, this is not the clean solution, and like a work around, but interface in Java are like that, that's why using abstract class is better choice, when evolution is concern. I think best way possible is to declare that method in another interface and let only classes needed that method implements new interface as well. adding method will result in breaking of all clients. Javin Connection refused exception in Interface is almost immutable, once published, any modification on interface e.g. I tried to give answer by making an abstract class to implement interface ABC, and then making each of client class to extend from Abstract class, but interviewer was not satisfied, he also raise concern, like what would happen if one of the client classes is already extend another class, Since in Java you can only extend one class, how would you solve that.

What would be your approach to make that change in minimal way to solve the problem of overriding that method in all implementing classes? Now you need to add another method in that interface ABC. Suppose you have an interface say ABC, which has been implemented by dozens of classes. It's a great course to understand the complete process of object-oriented analysis and design for creating quality software.Ĭan anyone please advise on Below question, I was recently asked this question on a Java Interview with Nomura Mumbai :

It’s mostly fact-based questions, but some questions like the difference between abstract class and interface in Java, and when to prefer abstract class over interface can be really tricky.ītw, if you are new to the world of object-oriented programming and design then I also suggest you go through a hands-on course like UML and Object-Oriented Design Foundations by Karloy Neisztor on Udemy. All questions have been asked in various Java interviews and the difficulty level for these questions is easy for most Java developers. They are mostly asked along with oth er Java design pattern questions, like the Decorator pattern or Factory pattern.Īnyway, in this article, we will see a mix of these interview questions from abstract class and interface. Interview questions from the abstract class are more common on junior level or you say under 2 years experience of Java programmers while interface-related questions are mostly asked on senior-level Java interview e.g. The interface is more common, because of its popularity among designers but questions from abstract class also pop up now and then. Abstract class and interface are very popular in any object-oriented programming language or Java interview, and there are always one or more questions from this.

Java constructor in abstract class