Java Intro PDF

# What is Java? - Java is a high-level, object-oriented programming language. - Java is platform-independent. - Java is mainly used for application programming. - It is widely used in: - Web applications - Mobile applications - Enterprise applications - Middleware applications # O...

# What is Java? - Java is a high-level, object-oriented programming language. - Java is platform-independent. - Java is mainly used for application programming. - It is widely used in: - Web applications - Mobile applications - Enterprise applications - Middleware applications # Object Oriented Programming vs. Procedural Programming | **Object Oriented Programming** | **Procedural Programming** | | --------------------------------- | ---------------------------- | | Bottom Up approach | Top Down Approach | | Divided into objects | Divided into functions | | Has Access Modifiers | Doesn't have Access Modifiers | | Objects can move & communicate with each other through member functions | Data can move freely from function to function in the system | | More secure | Less Secure | | Supports overloading | Do not support overloading | # Why We Need Programming Paradigms? "Any fool can write code that a computer can understand. Good programmers write code that humans can understand." - **Without understanding programming paradigms:** - Increase Complexity - Less Readability - Less Structure - Hard to Test - Hard to Change - Hard to Maintain # OOPS Features - Class - Object - Inheritance - Polymorphism - Encapsulation - Abstraction # Object Oriented Programming (OOPS) **Object-Oriented Programming** is a methodology or paradigm to design a program using **Classes and Objects**. - **Objects:** - Real world entities that has their own properties and behaviours. - **Example:** Class Dog - Properties: breed, size, age, color - Behaviour: eat(), sleep(), run(), bark() - **Classes:** - Blueprint from which an objects properties and behaviours are decided. # OOPS Concepts - **Object:** - Real World Entity - Properties - Tasks performed - Instance of class - Example: **Human** - Name - Color - Height - **Tasks:** walk(), run(), read(), write() - **Class:** - Blue Print that object follows - Number of objects - Example: **Student** - Properties: name, rollNo, DOJ - Tasks: read(), write(), play() - Objects: ABC, DEF, GHI - **Abstraction:** - Showing only Essential parts - Hiding the Implementation Details - **Example:** Android application - apk - exe - **Encapsulation:** - Binding Variables and Methods under single Entity - **Example:** - **Class:** - Name - Variables - Methods - **Student:** - name - rollNo - DOJ - **Tasks:** read(), write(), play() - **Inheritance:** - Acquiring the properties of one class to another class - **Super Class:** Parent Class - **Sub Class:** Child Class - **Base Class:** Derived Class - **Types of Inheritance:** - Single Inheritance - Multi-level Inheritance - Hierarchical Inheritance - **Polymorphism:** - Performing same Task in different ways & method - Example: - **drawPolygon()** - SQUARE - RECTANGLE - TRIANGLE - Types of Polymorphism: - **Method overloading:** Compile-time - **Method overriding:** Run-time