Installing JDK

What is JDK?

JDK (Java Development Kit) is a software development environment used to develop Java applications. It includes:

Java Compiler (javac): Converts Java code to bytecode
JRE (Java Runtime Environment): To run Java programs
Development Tools: Debugger, JavaDoc, jar, etc.
Java API Libraries: Pre-written code

Why Install JDK?

You need JDK to:

Write Java programs
Compile Java code (.java to .class)
Run Java applications
Debug and test Java programs

JDK vs JRE vs JVM

JDK (Java Development Kit):

For developers
Contains JRE + development tools
Used to develop Java applications

JRE (Java Runtime Environment):

For end users
Contains JVM + libraries
Used to run Java applications

JVM (Java Virtual Machine):

Executes bytecode
Part of JRE
Platform-specific

Relationship:

JDK = JRE + Development Tools
JRE = JVM + Library Classes

Types of JDK

1. Oracle JDK

Official JDK from Oracle
Commercial license for production
Free for development and personal use
Best support and updates

2. OpenJDK

Open source version
Free for all uses
Community-driven
Same features as Oracle JDK

3. Other Distributions

Amazon Corretto: AWS distribution
AdoptOpenJDK: Community builds
Azul Zulu: Enterprise JDK
IBM Semeru: IBM distribution

System Requirements

Minimum Requirements:

Operating System: Windows 7+, macOS 10.8+, Linux
RAM: 128 MB (minimum), 512 MB recommended
Disk Space: 200 MB
Processor: Pentium 2 or higher

Recommended:

RAM: 2 GB or more
Disk Space: 500 MB
Modern processor

Installing JDK on Windows

Step 1: Download JDK

Visit Oracle’s website: https://www.oracle.com/java/technologies/downloads/
Select your operating system (Windows)
Choose JDK version (Java 17 LTS or Java 21 LTS recommended)
Download the installer (.exe file)
Accept license agreement

Alternative: Download OpenJDK from https://adoptium.net/

Step 2: Run Installer

Double-click the downloaded .exe file
Click “Next” on welcome screen
Choose installation location (default: C:\Program Files\Java\jdk-xx)
Click “Next” to install
Wait for installation to complete
Click “Close” when finished

Step 3: Set Environment Variables

Why? So you can run Java commands from any directory.

Setting JAVA_HOME:

Right-click “This PC” or “Computer”
Select “Properties”
Click “Advanced system settings”
Click “Environment Variables”
Under “System variables”, click “New”
Variable name: JAVA_HOME
Variable value: C:\Program Files\Java\jdk-17 (your JDK path)
Click “OK”

Adding to PATH:

In System variables, find “Path”
Click “Edit”
Click “New”
Add: %JAVA_HOME%\bin
Click “OK” on all windows

Step 4: Verify Installation

Open Command Prompt and type:

java -version

Expected output:

java version "17.0.1" 2021-10-19 LTS
Java(TM) SE Runtime Environment (build 17.0.1+12-LTS-39)
Java HotSpot(TM) 64-Bit Server VM (build 17.0.1+12-LTS-39)

Check compiler:

javac -version

Expected output:

javac 17.0.1

Installing JDK on macOS

Step 1: Download JDK

Visit Oracle’s website or use Homebrew
Download macOS installer (.dmg file)

Using Homebrew (Recommended):

brew install openjdk@17

Step 2: Install

Manual Installation:

Open .dmg file
Run the installer package
Follow installation prompts
Enter admin password when prompted

Step 3: Set JAVA_HOME

Add to ~/.bash_profile or ~/.zshrc:

export JAVA_HOME=$(/usr/libexec/java_home)
export PATH=$JAVA_HOME/bin:$PATH

Reload:

source ~/.zshrc

Step 4: Verify

java -version
javac -version

Installing JDK on Linux (Ubuntu/Debian)

Method 1: Using APT (Recommended)

# Update package list
sudo apt update

# Install OpenJDK 17
sudo apt install openjdk-17-jdk

# Verify installation
java -version
javac -version

Method 2: Manual Installation

Download Linux tar.gz file
Extract:
```
tar -xzf jdk-17_linux-x64_bin.tar.gz
```
Move to /opt:
```
sudo mv jdk-17 /opt/
```

Set JAVA_HOME in ~/.bashrc:

export JAVA_HOME=/opt/jdk-17
export PATH=$JAVA_HOME/bin:$PATH

Reload:
```
source ~/.bashrc
```

Setting Up IDE (Optional but Recommended)

Popular Java IDEs:

IntelliJ IDEA
- Most popular
- Smart code completion
- Download: https://www.jetbrains.com/idea/
Eclipse
- Free and open source
- Large plugin ecosystem
- Download: https://www.eclipse.org/
VS Code
- Lightweight
- Install Java Extension Pack
- Download: https://code.visualstudio.com/
NetBeans
- Official Java IDE
- Good for beginners
- Download: https://netbeans.apache.org/

Common Installation Issues

Issue 1: “java is not recognized”

Problem: PATH not set correctly

Solution:

Check JAVA_HOME is set correctly
Ensure %JAVA_HOME%\bin is in PATH
Restart Command Prompt/Terminal
Restart computer if necessary

Issue 2: Wrong Java Version

Problem: Multiple Java versions installed

Solution:

Check JAVA_HOME points to correct version
Use where java (Windows) or which java (Mac/Linux)
Uninstall old versions

Issue 3: Permission Denied (Linux/Mac)

Problem: Insufficient permissions

Solution:

Use sudo for installation
Check file permissions
Run terminal as administrator

Choosing the Right JDK Version

For Learning (2024):

Java 17 LTS: Widely used, stable
Java 21 LTS: Latest LTS with modern features

For Production:

Java 11 LTS: Stable, mature
Java 17 LTS: Recommended for new projects
Java 21 LTS: Latest features

LTS (Long Term Support):

Java 8, 11, 17, 21
Receive updates for 3+ years
Recommended for production

Updating JDK

Windows:

Download new version installer
Run installer
Update JAVA_HOME if needed
Verify new version

macOS (Homebrew):

brew upgrade openjdk

Linux:

sudo apt update
sudo apt upgrade openjdk-17-jdk

Uninstalling JDK

Windows:

Control Panel → Programs → Uninstall
Find Java (TM) Development Kit
Click Uninstall
Remove JAVA_HOME from environment variables

macOS:

sudo rm -rf /Library/Java/JavaVirtualMachines/jdk-xx.jdk

Linux:

sudo apt remove openjdk-17-jdk

Testing Your Installation

Create a simple test program:

HelloWorld.java:

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("JDK installed successfully!");
    }
}

Compile:

javac HelloWorld.java

Run:

java HelloWorld

Output:

JDK installed successfully!

Exam Tips

Know the difference: JDK vs JRE vs JVM
JDK contains: JRE + Development Tools (javac, jar, etc.)
Environment variables: JAVA_HOME and PATH
Verification commands: java -version and javac -version
LTS versions: 8, 11, 17, 21 (Long Term Support)
JDK types: Oracle JDK (commercial), OpenJDK (open source)
Installation location: Usually in C:\Program Files\Java (Windows)
Why JAVA_HOME?: So tools can find Java installation

Important Points

JDK is required for development, JRE for running only
Always verify installation with java -version
Set environment variables for command-line access
Choose LTS version for stability
Keep JDK updated for security
One JDK can compile for older Java versions (backward compatibility)

Installing JDK

What is JDK?

Why Install JDK?

JDK vs JRE vs JVM

Types of JDK

1. Oracle JDK

2. OpenJDK

3. Other Distributions

System Requirements

Installing JDK on Windows

Step 1: Download JDK

Step 2: Run Installer

Step 3: Set Environment Variables

Step 4: Verify Installation

Installing JDK on macOS

Step 1: Download JDK

Step 2: Install

Step 3: Set JAVA_HOME

Step 4: Verify

Installing JDK on Linux (Ubuntu/Debian)

Method 1: Using APT (Recommended)

Method 2: Manual Installation

Setting Up IDE (Optional but Recommended)

Popular Java IDEs:

Common Installation Issues

Issue 1: “java is not recognized”

Issue 2: Wrong Java Version

Issue 3: Permission Denied (Linux/Mac)

Choosing the Right JDK Version

For Learning (2024):

For Production:

LTS (Long Term Support):

Updating JDK

Windows:

macOS (Homebrew):

Linux:

Uninstalling JDK

Windows:

macOS:

Linux:

Testing Your Installation

Exam Tips

Important Points

Install Notes App