This tutorial will explain you the Java OOP’S concepts.

OOP Definition

Learn Object Oriented Concepts for Android : Object-oriented programming (OOP) is a programming language model that allows users to create and organize Java applications on desktops.Writing object-oriented programs involves creating classes, objects and applications which are stand-alone executable programs that use those objects.It simplifies the software development and maintenance by providing some concepts

A few aspects of Object Oriented development,it can help to make the best of your Android projects,

  • Objects  and Classes
  • Inheritance
  • Interface
  • Encapsulation
  • Abstraction
  • Polymorphism

Let’s discuss what are the features of Object Oriented Programming,

Objects  and Classes

A class is a blueprint from which objects are created. It is a logical entity and the class contain field,methods,constructors,blocks , nested class  and interface.

Syntax

class <class_name>{  

   field;  

   method;  

}  

Object is an instance of class,it is the physical as well as logical entity whereas class is the logical entity only and objects have state and behaviour entity.

Syntax:

Classname objectname=new classname();

Inheritance

When one object acquires all the properties and behaviours of parent object known as inheritance. It provides code reusability and used to achieve runtime polymorphism.

The extends keyword indicates that you are making a new class that derives from an existing class.

Syntax

class Subclass-name extends Superclass-name  

{  

  //methods and fields  

}  

There are three types of inheritance in java: single, multilevel and hierarchical.

Interfaces

Multiple inheritance achieved through by interface. Interface is a collection of abstract methods. A class implements an interface, thereby inheriting the abstract methods of the interface. An interface does not contain any constructors.

The interface keyword is used to declare an interface

Syntax

public interface NameOfInterface {

  // Any number of final, static fields

  // Any number of abstract method declarations

}

Encapsulation

Encapsulation is a wrapping code and data together into a single unit. It keeps both safe from outside interference and misuse.If  declare the variables of a class as private.

Syntax

public int getter() {

     return value;

  }

public void setter()  

{

Variables = value;

  }

Abstraction

Abstraction is process of hiding the implementation details and showing only the functionality.

Syntax

public abstract class classname

{

Block of code

}

Polymorphism

Polymorphism is the ability of an object to take on many forms.Java has best support of polymorphism in terms of method overloading and method overriding

Method overloading

A class have multiple methods by same name but different parameter is known as Method Overloading.  It increases the readability of program and also called as compile time polymorphism

Method Overriding

When a method in a sub class has same name and type signature as a method in its super class, then the method is known as overridden method.It is also called runtime polymorphism

Advantages of OOPs

  • Objects created for Object Oriented Programs can easily be reused in other programs
  • It is good for defining abstract data types.
  • It is easy to maintain and modify existing code as new objects can be created with small differences to existing ones.
  • Object-oriented systems can be easily upgraded from small to large system

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