1. Installing the Java Development Kit (JDK)

1.1 What is JDK

JDK (Java Development Kit) is a software package that provides tools required to develop Java applications. It includes the compiler (javac), libraries, and runtime environment.

1.2 Choosing the Right JDK Version

• Beginners should use the latest LTS (Long-Term Support) version
• Common choices: Java 17 or Java 21

1.3 Downloading JDK

Download JDK from official sources like:

• Oracle JDK
• OpenJDK

1.4 Installation on Windows

• Download the .exe file
• Run the installer
• Follow setup instructions
• Note installation path

1.5 Installation on macOS

• Download .dmg file
• Install like a normal app
• Verify using terminal

1.6 Installation on Linux

• Use package manager (apt, yum)
• Example: sudo apt install openjdk-17-jdk

1.7 Verifying Installation

Open terminal/command prompt and run:

java -version
javac -version

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2. Understanding JDK, JRE, and JVM

2.1 Java Architecture Overview

Java works using a layered system:

• Source code → Bytecode → Execution

2.2 What is JVM

JVM (Java Virtual Machine) executes Java bytecode. It makes Java platform-independent.

2.3 What is JRE

JRE (Java Runtime Environment) provides libraries and JVM to run Java programs.

2.4 What is JDK

JDK includes:

• JRE
• Compiler (javac)
• Development tools

2.5 Differences

Component	Purpose
JVM	Runs bytecode
JRE	Provides runtime environment
JDK	Full development kit

2.6 How They Work Together

• Write code → Compile with JDK → Run using JVM (via JRE)

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3. Setting Environment Variables

3.1 What are Environment Variables

These are system variables that help your OS locate software like Java.

3.2 Why PATH is Important

PATH allows you to run Java commands from anywhere in the terminal.

3.3 Setting JAVA_HOME

JAVA_HOME points to your JDK installation directory.

3.4 Configuring PATH

Add JDK’s bin folder to PATH.

3.5 On Windows

• Open System Properties
• Go to Environment Variables
• Add:
  • JAVA_HOME = JDK path
  • PATH = %JAVA_HOME%\bin

3.6 On macOS/Linux

Edit .bashrc or .zshrc:

export JAVA_HOME=/path/to/jdk
export PATH=$JAVA_HOME/bin:$PATH

3.7 Verification

Run:

echo %JAVA_HOME%   (Windows)
echo $JAVA_HOME   (Mac/Linux)

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4. Installing an IDE

4.1 What is an IDE

An IDE (Integrated Development Environment) helps write, run, and debug code easily.

4.2 Popular IDEs

• IntelliJ IDEA
• Eclipse
• VS Code

4.3 Installing IntelliJ IDEA

• Download Community Edition
• Install and launch
• Create a new Java project

4.4 Installing Eclipse

• Download Eclipse Installer
• Choose “Eclipse IDE for Java Developers”

4.5 Installing VS Code

• Install VS Code
• Add Java Extension Pack

4.6 Configuring IDE

• Set JDK path
• Configure project SDK

4.7 Creating First Project

• Click “New Project”
• Select Java
• Choose JDK
• Create class file

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5. Writing and Running Your First Java Program

5.1 Structure of a Java Program

Basic structure:

• Class
• Main method

5.2 Main Method

Entry point of Java program:

public static void main(String[] args)

5.3 Hello World Program

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

5.4 Saving File

• Save as HelloWorld.java

5.5 Compiling

javac HelloWorld.java

5.6 Running

java HelloWorld

5.7 Running in IDE

• Click Run button
• Output appears in console

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6. Understanding the Compilation Process

6.1 Compilation Overview

Java uses a two-step process:

1. Compile
2. Execute

6.2 Source to Bytecode

• .java → .class

6.3 Role of javac

The compiler converts code into bytecode.

6.4 What is Bytecode

• Intermediate code
• Platform-independent

6.5 Role of JVM

JVM converts bytecode into machine code.

6.6 Platform Independence

“Write Once, Run Anywhere”
Java runs on any system with JVM.

6.7 Common Errors

• Syntax errors
• Missing semicolon
• Wrong file name
• Class name mismatch

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Conclusion

Setting up the Java environment may seem technical at first, but once completed, it becomes the foundation of your programming journey. With JDK installed, environment variables configured, and an IDE ready, you are fully prepared to start learning Java and building applications.