Tutorials References Exercises Videos Menu
Free Website Get Certified Upgrade

Java Tutorial

Java HOME Java Intro Java Get Started Java Syntax Java Output Java Comments Java Variables Java Data Types Java Type Casting Java Operators Java Strings Java Math Java Booleans Java If...Else Java Switch Java While Loop Java For Loop Java Break/Continue Java Arrays

Java Methods

Java Methods Java Method Parameters Java Method Overloading Java Scope Java Recursion

Java Classes

Java OOP Java Classes/Objects Java Class Attributes Java Class Methods Java Constructors Java Modifiers Java Encapsulation Java Packages / API Java Inheritance Java Polymorphism Java Inner Classes Java Abstraction Java Interface Java Enums Java User Input Java Date Java ArrayList Java LinkedList Java HashMap Java HashSet Java Iterator Java Wrapper Classes Java Exceptions Java RegEx Java Threads Java Lambda

Java File Handling

Java Files Java Create/Write Files Java Read Files Java Delete Files

Java How To

Add Two Numbers Count Words Reverse a String

Java Reference

Java Keywords Java String Methods Java Math Methods

Java Examples

Java Examples Java Compiler Java Exercises Java Quiz Java Certificate


Java OOP


Java - What is OOP?

OOP stands for Object-Oriented Programming.

Procedural programming is about writing procedures or methods that perform operations on the data, while object-oriented programming is about creating objects that contain both data and methods.

Object-oriented programming has several advantages over procedural programming:

  • OOP is faster and easier to execute
  • OOP provides a clear structure for the programs
  • OOP helps to keep the Java code DRY "Don't Repeat Yourself", and makes the code easier to maintain, modify and debug
  • OOP makes it possible to create full reusable applications with less code and shorter development time

Tip: The "Don't Repeat Yourself" (DRY) principle is about reducing the repetition of code. You should extract out the codes that are common for the application, and place them at a single place and reuse them instead of repeating it.


Java - What are Classes and Objects?

Classes and objects are the two main aspects of object-oriented programming.

Look at the following illustration to see the difference between class and objects:

class

Fruit

objects

Apple

Banana

Mango

Another example:

class

Car

objects

Volvo

Audi

Toyota

So, a class is a template for objects, and an object is an instance of a class.

When the individual objects are created, they inherit all the variables and methods from the class.

You will learn much more about classes and objects in the next chapter.