Oop programs examples

A class when declared using the keyword abstract is an abstract class in java. An abstract class is extended by other classes and the methods should be implemented. For example: From the above figure, the vehicle is an abstract class which is extended by SUV, Sedan, etc. An interface , in simple words, is a draft of a class which is used to achieve abstraction. Since an interface is similar to a class, it has variables and methods which are by default abstract.

For more detail about this topic, do read Java Program using Interface. The practice of combining data and operations into a single entity is defined as encapsulation. In Java, encapsulation can be illustrated by making the data member of class private and declare getter and setter methods to make it accessible. The class whose properties are used inherited is considered the parent or superclass. And the inheriting class is the child or subclass. Inheritance, in general, depicts the parent-child relationship in object-oriented programming, which is also called as the IS-A relationship.

There are 3 types of inheritance in Java. Java uses the extends keyword to implement the principle of inheritance in code. Besides the four main principles of OOP, Java also works with three further concepts association, aggregation, composition you can make use of when designing your programs.

Aggregation is a special form of association , while composition is a special form of aggregation. Association simply means the act of establishing a relationship between two unrelated classes.

For example, when you declare two fields of different types e. Car and Bicycle within the same class and make them interact with each other, you have performed association. Aggregation is a narrower kind of association. When you declare the Passenger class, you can create a field of the Car type that shows which car the passenger belongs to. Then, when you instantiate a new Passenger object, you can access the data stored in the related Car as well.

Composition is a stricter form of aggregation. For example, take a Car and an Engine class. With abstraction, you can hide the internal workings of an object and only show the features the user needs to know about.

Java provides two ways to implement abstraction: abstract classes and interfaces. An abstract class is a superclass parent class that cannot be instantiated. You need to instantiate one of its child classes if you want to create a new object. Abstract classes can have both abstract and concrete methods. Abstract methods contain only the method signature, while concrete methods declare a method body as well.

Abstract classes are defined with the abstract keyword. In the example below, you can see an abstract class called Animal with two abstract and one concrete method. Extend the Animal abstract class with two child classes: Bird and Fish.

Both of them set up their own functionality for the move and eat abstract methods. Now, test it with the TestBird and TestFish classes. Both call the one concrete label and the two abstract move and eat methods. In the console, the concrete method has been called from the Animal abstract class, while the two abstract methods have been called from Bird and Fish , respectively. For calling the instance method in a program, you should create an Object from the class that will provide accessibility of class members and attributes with the help of the dot operator.

The self represents the instance of the class. By using that, we will get superior access to our class methods and attributes. If it is also an optional keyword, we can declare whatever we need as an identifier. Therefore I will declare myself a keyword instead of self-keyword. Setattr obj, name — this method used to set an attribute.

If it created when it does not exist. Every class in python can retain below an attribute and access by using the dot operator. It will do some specific tasks and return a result to the requester.

Next, we define the object named "student" from our class named Dommy. When we call our instance method by the object, then the corresponding instance method will be executed and print. The remaining concepts, we will discuss in the next article. Stay tuned. View All. Elavarasan Rangaraj Updated date Feb 12, These variables are called Instance Variables or local variables.

One which is defined outside of methods are called Class Variables or global variables. You can access these variables anywhere in the class. See the difference in the example below. In the example below, we are creating class for cab. Both Cab and taxi means the same thing. Attributes or properties of cab is driver name, number of kilometers run by a cab, Pick-up and drop location, cab fare and number of passengers boarded cab.

Here we are creating 3 methods : rateperkm , noofcabs , avgnoofpassengers. First one is instance method and other two are class methods. In the script below, method can be called with no parameter ignoring phrase parameter. Or it can be called with parameter phrase. Deepanshu founded ListenData with a simple objective - Make analytics easy to understand and follow. He has over 10 years of experience in data science. During his tenure, he has worked with global clients in various domains like Banking, Insurance, Private Equity, Telecom and Human Resource.

Succinctly written! This certainly is a solid boot-camp course for a Noob like me in the wonderful world of python programming Write a pthon program using inheritance. I can't express my words how well it is useful for me.