Object Oriented Programming

What are the four pillars of OOP?

1. Encapsulation. Every Object maintains a private state inside a class. Other objects can not access this state directly, they can only invoke a list of public functions. The object manages its own state via these public functions and no other class can alter it unless explicitly allowed. In order to communicate with the object you will need to utilize the methods provided. 2. Abstraction. An extension of encapsulation. The process of selecting data from a larger pool to show only the relevant details to the object. The process of fetching / removing / selecting information from a larger pool of is referred to as abstraction. The power of Abstraction comes from the being able to utilize the the same pool of information use used for one one application for another. 3. Inheritance. The ability of one object to acquire some / all properties of another object. With Inheritance reusability is a major advantage. 4. Polymorphism. The way to use a class exactly like its parent so there is no confusion with mixing types. That being said each child sub-class keeps its own functions / methods as they are.

What is a Class in OOP?

A class is a blueprint for creating object, providing initial values for state (member variables or attributes) and implementations of behavior (member functions or methods) User defined objects are created using the class keyword. The class is a blueprint that defines a nature of a future object. Classes are used to create and manage new objects and support Inheritance.

What is an object in OOP?

A component of a program that knows how to perform certain actions and how to interact with other elements of the program. The basic unit of object oriented programming

What are access specifiers and what is their significance?

Access specifiers, as the name suggests, are a special type of keywords, which are used to control or specify the accessibility of entities like classes, methods, etc. Some of the access specifiers or access modifiers include "private", "public", etc. These access specifiers also play a very vital role in achieving Encapsulation - one of the major features of OOPs.

What is Object Oriented Programming?

An Approach to problem saving where all computations are carried out using objects.

How is data abstraction accomplished?

An abstract class is a special class containing abstract methods. The significance of abstract class is that the abstract methods inside it are not implemented and only declared. So as a result, when a subclass inherits the abstract class and needs to use its abstract methods, they need to define and implement them.

What is an exception?

An exception can be considered as a special event, which is raised during the execution of a program at runtime, that brings the execution to a halt. The reason for the exception is mainly due to a position in the program, where the user wants to do something for which the program is not specified, like undesirable input.

What is an interface?

An interface refers to a special type of class, which contains methods, but not their definition. Only the declaration of methods is allowed inside an interface. To use an interface, you cannot create objects. Instead, you need to implement that interface and define the methods for their implementation.

What is meant by dynamic polymorphism?

Dynamic Polymorphism or Runtime polymorphism refers to the type of Polymorphism in OOPs, by which the actual implementation of the function is decided during the runtime or execution. The dynamic or runtime polymorphism can be achieved with the help of method overriding.

What is a Method in OOP?

Functions / expressions that an object can perform. A human being the object, walking would be the method.

What is Abstraction

If you are a user, and you have a problem statement, you don't want to know how the components of the software work, or how it's made. You only want to know how the software solves your problem. Abstraction is the method of hiding unnecessary details from the necessary ones. It is one of the main features of OOPs. For example, consider a car. You only need to know how to run a car, and not how the wires are connected inside it. This is obtained using Abstraction.

Explain Inheritance with an example

Inheritance is one of the major features of object-oriented programming, by which an entity inherits some characteristics and behaviors of some other entity and makes them their own. Inheritance helps to improve and facilitate code reuse. Let me explain to you with a common example. Let's take three different vehicles - a car, truck, or bus. These three are entirely different from one another with their own specific characteristics and behavior. But. in all three, you will find some common elements, like steering wheel, accelerator, clutch, brakes, etc. Though these elements are used in different vehicles, still they have their own features which are common among all vehicles. This is achieved with inheritance. The car, the truck, and the bus have all inherited the features like steering wheel, accelerator, clutch, brakes, etc, and used them as their own. Due to this, they did not have to create these components from scratch, thereby facilitating code reuse.

How is an abstract class different from an interface?

Interface and abstract class both are special types of classes that contain only the methods declaration and not their implementation. But the interface is entirely different from an abstract class. The main difference between the two is that, when an interface is implemented, the subclass must define all its methods and provide its implementation. Whereas when an abstract class is inherited, the subclass does not need to provide the definition of its abstract method, until and unless the subclass is using it. Also, an abstract class can contain abstract methods as well as non-abstract methods.

What is meant by exception handling?

No one wants its software to fail or crash. Exceptions are the major reason for software failure. The exceptions can be handled in the program beforehand and prevent the execution from stopping. This is known as exception handling.So exception handling is the mechanism for identifying the undesirable states that the program can reach and specifying the desirable outcomes of such states. Try-catch is the most common method used for handling exceptions in the program.

Is it always necessary to create objects from class?

No. An object is necessary to be created if the base class has non-static methods. But if the class has static methods, then objects don't need to be created. You can call the class method directly in this case, using the class name.

What are some advantages of using OOP?

OOPs is very helpful in solving very complex level of problems. Highly complex programs can be created, handled, and maintained easily using object-oriented programming. OOPs, promote code reuse, thereby reducing redundancy. OOPs also helps to hide the unnecessary details with the help of Data Abstraction. OOPs, are based on a bottom-up approach, unlike the Structural programming paradigm, which uses a top-down approach. Polymorphism offers a lot of flexibility in OOPs.

Why is OOPs so popular?

OOPs programming paradigm is considered as a better style of programming. Not only it helps in writing a complex piece of code easily, but it also allows users to handle and maintain them easily as well. Not only that, the main pillar of OOPs - Data Abstraction, Encapsulation, Inheritance, and Polymorphism, makes it easy for programmers to solve complex scenarios. As a result of these, OOPs is so popular.

What is meant by Garbage Collection in OOPs world?

Object-oriented programming revolves around entities like objects. Each object consumes memory and there can be multiple objects of a class. So if these objects and their memories are not handled properly, then it might lead to certain memory-related errors and the system might fail. Garbage collection refers to this mechanism of handling the memory in the program. Through garbage collection, the unwanted memory is freed up by removing the objects that are no longer needed.

What is encapsulation?

One can visualize Encapsulation as the method of putting everything that is required to do the job, inside a capsule and presenting that capsule to the user. What it means is that by Encapsulation, all the necessary data and methods are bind together and all the unnecessary details are hidden to the normal user. So Encapsulation is the process of binding data members and methods of a program together to do a specific job, without revealing unnecessary details. Encapsulation can also be defined in two different ways: 1) Data hiding: Encapsulation is the process of hiding unwanted information, such as restricting access to any member of an object. 2) Data binding: Encapsulation is the process of binding the data members and the methods together as a whole, as a class.

What is the difference between overloading and overriding?

Overloading is a compile-time polymorphism feature in which an entity has multiple implementations with the same name. For example, Method overloading and Operator overloading. Whereas Overriding is a runtime polymorphism feature in which an entity has the same name, but its implementation changes during execution. For example, Method overriding.

What is Polymorphism?

Polymorphism is composed of two words - "poly" which means "many", and "morph" which means "shapes". Therefore Polymorphism refers to something that has many shapes. In OOPs, Polymorphism refers to the process by which some code, data, method, or object behaves differently under different circumstances or contexts. Compile-time polymorphism and Run time polymorphism are the two types of polymorphisms in OOPs languages.

What are the various types of inheritance?

Single inheritance Multiple inheritances Multi-level inheritance Hierarchical inheritance Hybrid inheritance

What is meant by static polymorphism?

Static Polymorphism is commonly known as the Compile time polymorphism. Static polymorphism is the feature by which an object is linked with the respective function or operator based on the values during the compile time. Static or Compile time Polymorphism can be achieved through Method overloading or operator overloading.

Define a superclass?

Superclass is also a part of Inheritance. The superclass is an entity, which allows subclasses or child classes to inherit from itself.

What is a subclass?

The subclass is a part of Inheritance. The subclass is an entity, which inherits from another class. It is also known as the child class.

What is Inheritance?

The term "inheritance" means "receiving some quality or behavior from a parent to an offspring." In object-oriented programming, inheritance is the mechanism by which an object or class (referred to as a child) is created using the definition of another object or class (referred to as a parent). Inheritance not only helps to keep the implementation simpler but also helps to facilitate code reuse.

What is a Instance in OOP?

What is a Instance in OOP? An Instance is a specific object created from a particular class

Are there any limitations of Inheritance?

Yes, with more powers comes more complications. Inheritance is a very powerful feature in OOPs, but it has some limitations too. Inheritance needs more time to process, as it needs to navigate through multiple classes for its implementation. Also, the classes involved in Inheritance - the base class and the child class, are very tightly coupled together. So if one needs to make some changes, they might need to do nested changes in both classes. Inheritance might be complex for implementation, as well. So if not correctly implemented, this might lead to unexpected errors or incorrect outputs.