Java Programming for Beginners 🚀

Introduction

Instructor: Farhan Hassin Choudhry
Platform: FreeCodeCamp
Tool Used: Replit (an online IDE)
Goal: Learn fundamental concepts of Java programming
Pre-requisites: None, everything will be demonstrated within the browser

Setting Up

Replit Account: Create or log into your Replit account at www.replit.com.
Creating a Java Project: Use the Create button to start a new Java Repl project. Name it descriptively, like HelloWorld.
Interface: Adjust settings like layout to your preference (side-by-side or stacked).
Running Code: Click the Run button to compile and execute Java code.

Hello World Program

Java Source Files: End with .java and compiled files end with .class.
Structure: A basic Java program has a class declaration, a main method declared as public static void main(String[] args).
Printing to Console: Use System.out.println("Hello, World!");.

Variables and Data Types

Types: Primitive (int, byte, short, long, float, double, boolean, char) and Non-Primitive/Reference (Strings, Arrays).
Declaration and Initialization: Variable type, name, and value assignment.
Example: int age = 27;
Default Values: Numeric types default to 0, boolean defaults to false.
Type Conversion: Implicit (smaller to larger type) and explicit (larger to smaller type).

Operators

Types of Operators

Arithmetic Operators: +, -, *, /, %
Assignment Operators: =, +=, -=, *=, /=
Relational Operators: ==, !=, >, <, >=, <=
Logical Operators: &&, ||, !
Increment/Decrement Operators: ++, --

Examples

Example of Arithmetic Operators:
```
int sum = 10 + 5; // 15
```

Loops

For Loop

Structure: for(initialization; condition; update)
Example: for(int i = 0; i < 10; i++) { System.out.println(i); }

While Loop

Structure: while(condition)
Example: int i = 0; while(i < 10) { System.out.println(i); i++; }

Do-while Loop

Structure: do { // code } while(condition);
Example: int i = 0; do { System.out.println(i); i++; } while(i < 10);

Conditional Statements

If-Else

Structure: if (condition) { // code } else { // code }

Example:

int score = 85;
if (score >= 90) {
    System.out.println("A grade");
} else if (score >= 80) {
    System.out.println("B grade");
} else {
    System.out.println("C grade");
}

Switch-Case

Structure: switch (variable) { case x: // code; break; ... default: // code }

Example:

int day = 2;
switch (day) {
    case 1:
        System.out.println("Monday");
        break;
    case 2:
        System.out.println("Tuesday");
        break;
    // other cases
    default:
        System.out.println("Other day");
}

Arrays

Declaration: dataType[] arrayName = new dataType[size];
Initialization: arrayName[index] = value;

Example:

int[] numbers = new int[5];
numbers[0] = 10;

Enhanced For Loop: for(dataType item : arrayName) { // code }

Object-Oriented Programming (OOP)

Classes and Objects

Class: Template for objects.
Object: Instance of a class.

public class User {
    public String name;
    public LocalDate birthdate;

    public User(String name, String birthdate) {
        this.name = name;
        this.birthdate = LocalDate.parse(birthdate);
    }

    public int getAge() {
        return Period.between(this.birthdate, LocalDate.now()).getYears();
    }
}

Inheritance

Super Class (Parent): class SuperClass { ... }
Sub Class (Child): class SubClass extends SuperClass { ... }

Example:

public class AudioBook extends Book {
    private int runTime;

    public AudioBook(String title, String author, int runTime) {
        super(title, author);
        this.runTime = runTime;
    }
}

Conclusion

Practice: Key to mastering Java and OOP concepts.
Explore: Continue experimenting with examples and projects to solidify understanding.