File Name: oops interview questions and answers in java .zip
OOPS stands for Object-oriented programming, is a programming pattern based on the idea of "objects", which may comprise data, in the form of fields, frequently known as attributes; and code, in the form of procedures, often identified as methods.
Abstraction is a concept of showing only important information and hiding its implementation. This is one of the most asked Oops interview questions as it checks basic oops concepts for java programmers. For example: When you see a car, you know it is running but how it running internally, you may not aware of it.
Thanks, glad to hear that you like this list of Java Object Oriented Programming question. Would you like to add any more on this list? These are really basis Object Oriented Programming questions, anyone with just a couple of years experience and even a computer science graduates can can answer these question. I am looking for more challenging, tough and really difficult object oriented design questions which will test your knowledge and skill and not the definitions.
For example how would you go about designing - an e-commerce site like Amazon or FlipKart - how does Google work? Can you implement solution like that - Design an electronic trading system - design a washing machine etc. That would be less about Java and more about advanced programming algorithms, data structures, etc.
Also, I have shared a lot of system design questions which is like the questions you have mentioned in the list, you can check them here. Q: Can we override a non-static method as static in Java? A: No.. I think, 1 answer is wrong. I'm pasting question along with answer as follows: Can we override a non-static method as static in Java?
The compiler giver below error msg : "This static method cannot hide the instance method from InheritanceTest". Yes guys, you are right, it's not possible to override an instance method as static method in Java.
Thanks for pointing that out. Can we override a non-static method as static in Java? Yes Ajay, you are right, it's not possible to override a non-static method as static in Java. You answered it Yes. But it's not true. Both methods need to be either static or non-static.
You can't remove staticness of a method in sub class. Yes, you are right, Java doesn't allow you to override a non-static or instance method as static, I'll further check and correct. Thanks for pointing that error guys. Can we change the argument list of an overriding method? The argument list is part of the method signature and both overriding and overridden method must have the same signature.
Can you please explain the answer what do you mean by argument list in overriding we can change the order of argument , number of argument then what is this argument list.
Overall good collection Hello Surendra, what is your point here? Did you tried that on Eclipse or any other IDE? No we can't it will compilation error. Feel free to comment, ask questions if you have any doubt. Pages Home core java spring online courses thread java 8 coding sql books oop interview certification free resources best. Java is an object-oriented programming language and you will see a lot of object-oriented programming concept questions on Java interviews.
The classic questions like the difference between an interface and abstract class are always there but from the last couple of years more sophisticated questions based upon advanced design principles and patterns are also asked to check OOP knowledge of the candidate. Though, Object-oriented programming questions are more popular on Java interviews for 1 to 3 years experienced programmers. If you look for Java interview questions for 2 to 4 years experienced programmer, you will find lots of questions based upon OOP fundamentals like Inheritance and Encapsulation but as you gain more experience, you will see questions based on object-oriented analysis and design e.
What is method overloading in OOP or Java? When we have multiple methods with the same name but different functionality then it's called method overloading. For example. What is the method overriding in OOP or Java? In order for method overriding, we need Inheritance and Polymorphism, as we need a method with the same signature in both superclass and subclass. A call to such a method is resolved at runtime depending upon the actual object and not the type o variable. See the answer for a more detailed discussion.
What is the method of hiding in Java? Is Java a pure object-oriented language? Also, primitive variables are not objects in Java. See the answer for a more detailed explanation. What are the rules of method overloading and overriding in Java? Simply changing the return type of two methods will not result in overloading, instead, the compiler will throw an error. On the other hand, method overriding has more rules e. See the answer for a full list of rules related to method overloading and overriding in Java.
The difference between method overloading and overriding? The compiler only used the class information for method overloading, but it needs to know the object to resolved overridden method calls. This diagram explains the difference quite well, though:. What problem is solved by the Strategy pattern in Java? Strategy pattern allows you to introduce a new algorithm or new strategy without changing the code which uses that algorithm.
For example, the Collections. Since every object uses a different comparison strategy you can compare various objects differently without changing the sort method.
The decorator pattern takes advantage of Composition to provide new features without modifying the original class. A very good to-the-point question for the telephonic round. This is quite clear from the UML diagram of the Decorator pattern, as you can see the Component is associated with a Decorator. When to use the Singleton design pattern in Java? It's not free of cost though because it increases the coupling between classes and makes them hard to test.
This is one of the oldest design pattern questions from Java interviews. Please see the answer for a more detailed discussion. What is the difference between State and Strategy Patterns? The state pattern is used to do something specific depending upon state while Strategy allows you to switch between algorithms without changing the code which uses it. It has two forms, aggregation, and composition. For example, the city is an aggregation of people but is the composition of body parts.
What is the difference between Decorator, Proxy and Adapter pattern in Java? The Decorator adds additional functionality without touching the class, Proxy provides access control and Adapter is used to make two incompatible interfaces work together. This is another great OOPS concept question because it tests what matters, both of them are very important from a class design perspective.
Though both Composition and Inheritance allows you to reuse code, formerly is more flexible than later. Composition allows the class to get an additional feature at runtime, but Inheritance is static. You can not change the feature at runtime by substitution of a new implementation. That's all about in this list of object-oriented programming or OOPS concept interview questions. But, as I said, if you are a senior Java developer then you focus more on object-oriented analysis and design and learn how to code against a requirement using all your OOP knowledge.
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Download PDF We have compiled the most frequently asked Java Interview Questions and Answers that will help you prepare for the Basic Java interview questions that an interviewer might ask you during your interview. In this list of Basic Java interview questions, we have covered all commonly asked basic and advanced Core Java interview questions with detailed answers to help you clear the job interview. The following list contains important Core Java interview questions for freshers as well as Java interview questions and answers for experienced programmers to help them prepare for the interview. This detailed guide of interview questions for Java Programming will help you to crack your Job interview easily. What is the difference between an Inner Class and a Sub-Class? Ans: An Inner class is a class which is nested within another class. An Inner class has access rights for the class which is nesting it and it can access all variables and methods defined in the outer class.
By Priya Pedamkar. Oops, popularly known as Object-Oriented Programming techniques is the programming paradigm that revolves around the concept of objects. In an OOP language such as Java, everything is an object which contains data, fields, attributes and we code them in the form of procedures, also known as methods. It also comprises of class-based parameters which provide meaning to instances, determinant on their type. Oops, revolve around the basic concepts of Abstraction, Polymorphism, Inheritance, Encapsulation, Objects, classes, and interfaces. Here in this post, we have compiled a list of most commonly asked and important Oops Java interview questions and answers.
It refers to the languages which are using objects in programming. The objective of OOPS is to carry out practical entities such as hiding, abstraction, polymorphism, and more into coding. If you are new to OOPS or want to improve your skills. While implementing these entities, OOPS aims to increase the efficiency of code by binding the data and its functions needed for operation in such a way that accessibility to data remains limited to the functions which need them, thus, keeping your code extremely organized. Here in this article, we will be listing frequently asked OOPS interview questions and Answers with the belief that they will be helpful for you to gain higher marks.
Encapsulation : It is the mechanism that binds together code and data in manipulates, and keeps both safe from outside interference and misuse. In short it isolates a particular code and data from all other codes and data. A well-defined interface controls the access to that particular code and data. Inheritance : It is the process by which one object acquires the properties of another object.
Thanks, glad to hear that you like this list of Java Object Oriented Programming question. Would you like to add any more on this list? These are really basis Object Oriented Programming questions, anyone with just a couple of years experience and even a computer science graduates can can answer these question.
This post on Java Interview Questions is prepared with basic and important concepts of Java with examples for your easy understanding. When you start learning Java , the first method you encounter is public static void main String  args. The starting point of any Java Program is the main method. It is one of the important methods of Java. Technically, the main method is the starting point where the Java program starts its execution. JVM always look for this method signature to start running an application. Check this to know detailed explanation.
The picture show an overview of all the topics we would cover in this article on interview questions. Every class in java is a sub class of the class Object. When we create a class we inherit all the methods and properties of Object class. Actor reference variables actor1, actor2 hold the reference of objects of sub classes of Animal, Comedian and Hero.
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Ans: Encapsulation is a concept in Object Oriented Programming for combining properties and methods in a single unit. Encapsulation helps.Reply
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