OOPS is abbreviated as Object Oriented Programming system in which Top 50 OOPs Interview Questions & Answers .. Download PDF. What is OOPS? OOPS is abbreviated as Object Oriented Programming system in which programs are considered as a collection of objects. OOPS Interview Questions and Answers for Experienced In PHP, OOPs Concepts Interview Questions, PHP OOPs Interview Questions, OOPs.
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What is Object Oriented Programming? Object Oriented Programming (OOP) is a programming paradigm where the complete software operates as a bunch of. Object-oriented programming (OOPS) interview questions and answers in java: This post covers all topic include polymorphism, abstraction. In this article, we will discuss important OOPS interview questions and answers for beginners and experienced. This article describes some.
A class is a template for an object, a user-defined datatype that contains variables, properties, and methods. Object in programming is similar to real word object. Every programming object has some properties and behaviors.
Suppose we have a class Person which has attributes and methods like name, age, height, weight, color etc. Constructor is a special type of function which will be called automatically whenever there is any object created from a class. Destructor is a special type of function which will be called automatically whenever any object is deleted or goes out of scope. Purpose of Private Constructor: It ensures that there can be only one instance of a Class and provides a global access point to that instance and this is common with The Singleton Pattern.
This data will be invisible to the outside of the class and can be accessed via member functions. These variables are called attribute of the object once an object is created. When inheriting from an abstract class, all methods marked abstract in the parent's class declaration must be defined by the child; additionally, these methods must be defined with the same or a less restricted visibility.
Above Code define a TV class.
The class TV is an abstraction of a real TV in a very simple use case. Class properties and constants are not implemented, instead, they are declared, which in a way already makes them abstract.
They follow the same rules and are treated the same way when declared in an abstract class as they would any other class. Suppose we were modeling the behavior of animals, by creating a class hierarchy that started with a base class called Animal. Animals are capable of doing different things like flying, digging and walking, but there are some common operations as well like eating and sleeping.
Some common operations are performed by all animals, but in a different way as well.
When an operation is performed in a different way, it is a good candidate for an abstract method forcing subclasses to provide a custom implementation. It is simply "One thing, can use in different forms".
Technically, it is the ability to redefine methods for derived classes. Polymorphism could be static and dynamic both. What is Polymorphism?
Polymorphism means that some code or operations or objects behave differently in different contexts. Compile Time Polymorphism: Compile time polymorphism means compiler knows which function should be called when a polymorphic call is made.
Run Time Polymorphism: Run time polymorphism is supported by virtual functions.
The idea is, virtual functions are called according to the type of object pointed or referred, not according to the type of pointer or reference. In other words, virtual functions are resolved late, at runtime. What is Inheritance? What is the purpose? The idea of inheritance is simple, a class is based on another class and uses data and implementation of the other class.
The purpose of inheritance is Code Reuse. What is Abstraction? Explain different types of Polymorphism in Java Compile time polymorphism or method overloading or static banding Runtime polymorphism or method overriding or dynamic binding 1.
In this process, an overridden method is called through the reference variable of a superclass. The determination of the method to be called is based on the object being referred to by the reference variable.
What is Inheritance and give real-world examples? Definition Inheritance - IS-A relationship between a superclass and its subclasses. The process where one object acquires the members of another; plus can have its own. Real world example Dog subclass is-a of type Animal superclass. So Dog can inherit reuse members of Animal class; plus it can have its own new behavior and properties.
In the Java library, you can see extensive use of inheritance. Below figure shows a partial inheritance hierarchy from a java. What is the difference between Abstraction and Encapsulation? Abstraction provides a general structure of a class and leaves the details for the implementers. Encapsulation is to create and define the permissions and restrictions of an object and its member variables and methods. Abstraction is implemented in Java using interface and abstract class while Encapsulation is implemented using four types of access level modifiers: public, protected, no modifier and private.
What is multiple inheritance? A child class inheriting states and behaviors from multiple parent classes is known as multiple inheritance.
What is the diamond problem in inheritance?
In case of multiple inheritance, suppose class A has two subclasses B and C, and class D has two super classes B and C. This problem is known as the diamond problem.
Why Java does not support multiple inheritance? Java was designed to be a simple language and multiple inheritance introduces complexities like the diamond problem. Inheriting states or behaviors from two different type of classes is a case which in reality very rare and it can be achieved easily through an object association.
What is Static Binding and Dynamic Binding? Static or early binding is resolved at compile time. Method overloading is an example of static binding. Dynamic or late or virtual binding is resolved at runtime. Method overriding is an example of dynamic binding. What is Composition? A Composition is an association represents a part of a whole relationship where a part cannot exist without a whole.
If a whole is deleted then all parts are deleted. It has a stronger relationship. Read more about Composition with a complete example at Composition in Java with Example.
What is Aggregation? Aggregation is an association represents a part of a whole relationship where a part can exist without a whole. It has a weaker relationship. It is a specialized form of Association where all object has their own lifecycle but there is ownership. A Teacher may belong to multiple departments.
Hence Teacher is a part of multiple departments. But if we delete a Department, Teacher Object will not destroy.