Java Course Lecture Notes

Introduction

• Instructor: Mosh, a software engineer with 20 years of experience.
• Course Overview:
  • Install necessary tools for Java application development.
  • Learn Java basics, code execution, and algorithms.
  • Tips and shortcuts from professional experience.
  • Designed for beginners; no prior experience needed.
  • Write your first Java program in minutes.

Tools Installation

1. Java Development Kit (JDK):

   • Search for "jdk download" in the browser.
   • Download appropriate version from Oracle for your OS.
   • Installation process involves accepting the license, downloading the file, and following the installation wizard.

2. Code Editor:

   • Recommended: IntelliJ IDEA (Community Edition).
   • Download and install it for free.

Anatomy of a Java Program

• Functions: Smallest building blocks in Java, performing specific tasks.
  • Example functions: sending emails, converting weight.
• Function Syntax:
  • Return Type (e.g., void) Function Name (e.g., sendEmail)
  • Parameters within parentheses (e.g., String email)
  • Code block enclosed in curly braces.
• Main Function: Entry point of any Java program (must be public, static, and void).
• Classes: Containers for functions; every Java program must have at least one class containing the main function.
• Access Modifiers: Control visibility (e.g., public, private).

Creating a Java Project

• Create a new project in IntelliJ:
  • Select Java and make sure SDK version is correct.
  • Set up command-line application template.
  • Set base package name (e.g., com.codewithmosh).
• Writing Your First Java Program:
  • Structure: Package statement, class definition, main method, and print statement.
  • Use System.out.println("Hello, World!") to output.

Code Execution Process

1. Compilation: Converts Java code into bytecode using the Java compiler.
2. Execution: Java Virtual Machine (JVM) executes the bytecode platform independently.

Interesting Facts About Java

• Developed by James Gosling in 1995 at Sun Microsystems.
• Four editions: Java SE, Java EE, Java ME, Java Card.
• Approximately 9 million Java developers worldwide.
• Average salary of a Java developer is over $100,000 in the US.

Course Structure Overview

• Part 1: Fundamentals of Java programming.
• Part 2: Object-oriented programming.
• Part 3: Core Java APIs.
• Part 4: Advanced Java features (streams, threads, database programming).

Variables in Java

• Variable Declaration: Type name = value (e.g., int age = 30;).
• Types: Primitive (e.g., int, float, char, boolean) and Reference types (e.g., String).
• Variables must be initialized before use.

Control Flow Statements

• If Statements: For decision making based on conditions.
• Switch Statements: An alternative to if statements for multiple conditions.
• Loops: For executing code repeatedly (for, while, do-while, for-each).

Functions and Methods

• Functions are reusable code blocks that can take parameters and return values.
• Methods belong to classes; access modifiers control visibility.

Error Handling

• Validate user input to prevent errors in programs.
• Example: Using loops to keep asking for valid input (e.g., mortgage calculator).

Clean Code Principles

• Write code that is easy to read and maintain.
• Avoid repetition (DRY principle) and use meaningful variable names.

Conclusion

• Java is a powerful and widely used programming language.
• The course is structured to build a solid foundation for beginners.
• Encourage practice and engagement with the material.