Java for Beginners Course Notes

Instructor Introduction

• Farhan Hassin Ch: Experienced software developer at Free Code Camp.
• Course focuses on teaching Java fundamentals.

Course Setup

• Use Replit (an online IDE) for coding in Java.
• Account Setup: Create or log in to Replit.
• Create a new Replit project, select Java, and name it descriptively.

First Java Program: Hello World

• The default project contains a Hello World program:

  public class Main {
      public static void main(String[] args) {
          System.out.println("Hello, World!");
      }
  }
  

• Components of the program:
  • Class Declaration: public class Main
  • Main Method: Entry point for Java programs.
  • Printing Output: System.out.println() is used to print to the console.

Variables and Data Types

• Variable Declaration:
  • Syntax: type variableName;
  • Example: int age;
• Data Types in Java:
  • Primitive Types: byte, short, int, long, float, double, char, boolean.
  • Reference Types: Objects, arrays, etc.
• Variable Initialization:
  • Declare and assign:

    int age = 27;
    

Operators in Java

• Arithmetic Operators: + (addition), - (subtraction), * (multiplication), / (division), % (modulo).
• Assignment Operators: +=, -=, etc. (e.g., number += 5;)
• Relational Operators: ==, !=, >, <, >=, <=.
• Logical Operators: && (and), || (or), ! (not).

Control Flow

• If-Else Statements: Used to execute code based on conditions.
• Switch Statements: Alternative to if-else for multiple conditions.

Loops

• For Loop: Iterates over a block of code a set number of times.
• While Loop: Repeats a block while a condition is true.
• Do-While Loop: Similar to while but guarantees at least one execution.
• Enhanced For Loop: Simplifies iterating over arrays or collections.

Methods

• Defining Methods:
  • Syntax: returnType methodName(parameters) { /* code */ }
• Method Overloading: Same method name, different parameters.

Arrays

• Declaration:

  int[] numbers = new int[5];
  

• Accessing Elements: Use index (e.g., numbers[0]).
• Array Length: numbers.length
• Sorting and Searching: Use Arrays.sort() and Arrays.binarySearch().

ArrayLists

• Dynamic Lists: Use ArrayList<Type> for resizable arrays.
• Common Methods: add(), remove(), clear(), size(), contains(), get(), set().

HashMaps

• Key-Value Pairs: Use HashMap<KeyType, ValueType>.
• Common Methods: put(), get(), remove(), containsKey(), containsValue(), size(), clear().

Object-Oriented Programming (OOP)

• Classes and Objects: Blueprint for creating objects.
• Encapsulation: Keeping properties private and accessible via methods (getters/setters).
• Inheritance: Extending classes to create new classes.
• Constructors: Special methods for initializing objects.

Sample Classes

• User Class: Stores user information and methods to manage user data.
• Book Class: Base class for different book types with common properties.
• AudioBook and EBook Classes: Extend Book class with unique properties.

Conclusion

• Practice is essential for mastering Java and OOP concepts.
• Continue building projects to solidify understanding.