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Core Java - Interview Questions and Answers for 'Oops concept' - 57 question(s) found - Order By Rating | ||||
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Ans. No | ||||
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Ans. There is one VTable for each class. | ||||
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Like Discuss Correct / Improve  virtual table method  vtable  runtime polymorphism  object oriented programming (oops)  oops concepts   method overriding intermediate   rare | ||||
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This question is still unanswered. Can you please provide an answer. | ||||
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This question is still unanswered. Can you please provide an answer. | ||||
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Ans. 1. Enforcing composition over inheritance 2. Restricting overriding of certain methods 3. Final methods are faster than regular instance methods 4. Enforcing Immutability | ||||
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Like Discuss Correct / Improve  final class   reasons for final class   restricting inheritance  object oriented programming (oops)  oops concepts expert | ||||
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Ans. Yes, to a certain extent. But the objective for Final class could be beyond just enforcing composition as certain classes might have been created without inheritance or composition in mind. | ||||
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Ans. No | ||||
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Ans. Encapsulation facilitate hiding and restricted access and hence more of a security feature. Encapsulation is definitely a great feature as when applications expand criss cross communication between objects / modules could lead to blunders. Inheritance facilitates code reuse. Polymorphism comprise of method overloaded ( which to me is negligible usage ) and method overriding. Method overriding is of great usage as it facilitates concept of interfaces and plugin development. So it’s Security / Organization vs Code Reuse / Support for other features like overriding vs Contracts / Plugin Development facilitating the creation of frameworks / libraries. Which is more important may vary from application to application , its scale , its use , its sensitivity etc. | ||||
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Ans. Method overloading / static polymorphism compared to method overriding / runtime polymorphism has very limited usage as it just opens up an alternate way of defining a different method with the same name. Method Overriding on other hand opens up many other features like contracting , interfacing , pluging development and hence development of libraries and frameworks. | ||||
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Ans. Encapsulation facilitates security by hiding data and logic whereas Abstraction simplifies organization of data and related logic. As applications scale, both concepts are required for easy management and maintenance. Encapsulation for security and criss cross communication between objects / modules will make it vulnerable. and Abstraction for better organization that enables better understanding of application code and easy maintainability. | ||||
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Ans. 1. State Instance variable or member elements forms the object state. 2. Behavior Member functions forms the object behavior 3. Identity Every object has a unique identity within JVM through a unique Id. | ||||
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Ans. Overriding refers to the Methods with same name and parameters, such that the later over rides the former method. | ||||
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This question was recently asked at 'MST Solutions'.This question is still unanswered. Can you please provide an answer. | ||||
Sample Code for composition | ||||
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Ans. There are four main OOP concepts in Java. These are: Abstraction. Abstraction means using simple things to represent complexity. We all know how to turn the TV on, but we don?t need to know how it works in order to enjoy it. In Java, abstraction means simple things like objects, classes, and variables represent more complex underlying code and data. This is important because it lets avoid repeating the same work multiple times. Encapsulation. This is the practice of keeping fields within a class private, then providing access to them via public methods. It?s a protective barrier that keeps the data and code safe within the class itself. This way, we can re-use objects like code components or variables without allowing open access to the data system-wide. Inheritance. This is a special feature of Object Oriented Programming in Java. It lets programmers create new classes that share some of the attributes of existing classes. This lets us build on previous work without reinventing the wheel. Polymorphism. This Java OOP concept lets programmers use the same word to mean different things in different contexts. One form of polymorphism in Java is method overloading. That?s when different meanings are implied by the code itself. The other form is method overriding. That?s when the different meanings are implied by the values of the supplied variables. See more on this below. | ||||
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This question was recently asked at 'Intel'.This question is still unanswered. Can you please provide an answer. | ||||
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Ans. Abstraction is a process of hiding the implementation details and describing only the functionality to the user. | ||||
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Ans. Yes, Runtime Polymprohism requires either Class inheritance or Interface implementation. | ||||
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Ans. Loose Coupling Facilitates designing complex applications by making them modular. | ||||
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Ans. Getting parent class object properties into child class is called Inheritance. The process of representing one form into multiple forms is called polymorphism. | ||||
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Ans. You can implement encapsulation in Java by keeping the fields (class variables) private and providing public getter and setter methods to each of them. Java Beans are examples of fully encapsulated classes. Encapsulation in Java: Restricts direct access to data members (fields) of a class. | ||||
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Very frequently asked. Usually among very first few questions. | ||||
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Ans. Encapsulation is a feature of OOP's that binds the data and it's associated methods together as a single unit and facilitate protection and data hiding by providing minimal interface to outside. For example - member variables are declared private and are accessed through public methods. Moreover we have private methods that can only be used internally and hence providing minimal interface to outside class through use of public methods. | ||||
Sample Code for encapsulation | ||||
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Ans. By encapsulating it within another class and declaring it private. In such a case, it will only be accessible through parent class or parent class object. | ||||
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Ans. Private variables are not inherited. They are simply ignored and not made part of the derived object body. | ||||
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Ans. Dynamic dispatch in java is also known as runtime polymorphism.It is a process in which a call to an overriden method is resolved at runtime. | ||||
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Ans. dynamic method dispatch is a process in which a call to an overridden method is resolved at runtime rather than at compile-time. This is used to achieve runtime polymorphism in java. | ||||
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Ans. Java identifies the method to be called at runtime by the object that is being referenced. | ||||
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Like Discuss Correct / Improve  polymorphism  object oriented programming (oops)  oops concepts  overloading  overriding basic | ||||
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Ans. runtime polymorphism or method overriding doesn't require method name and signature to be different whereas compile time polymorphism or method overloading requires method name to be same but the signature to be different. | ||||
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Ans. Composition and Inheritance are the different types of Associations for Classes. Composition is a has-a association between classes. Inheritance is a is-a association between classes. | ||||
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Ans. Abstraction, Encapsulation, Polymorphism , Composition and Inheritance | ||||
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Ans. class A { void test() { System.out.println("test() method"); } } class B { void test() { System.out.println("test() method"); } } Suppose if Java allows multiple inheritance like this, class C extends A, B { } A and B test() methods are inheriting to C class. So which test() method C class will take? As A & B class test() methods are different , So here we would Facing Ambiguity. | ||||
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