Java Environment Setup: Installing JDK 21 LTS, Configuring PATH & IDEs

To begin coding in Java, you need two fundamental tools on your computer: the Java Development Kit (JDK) to compile and run your source code, and a reliable Integrated Development Environment (IDE) or text editor to write your programs.

Step 1: Downloading & Installing JDK 21+ LTS

We recommend installing Eclipse Temurin 21 (Adoptium) or Oracle OpenJDK 21. Follow these instructions for your platform:

Step 2: Configuring JAVA_HOME & PATH Manually (Windows)

If the installer did not configure environment variables automatically, follow these manual steps:

1. Press Win + R, type sysdm.cpl, and press Enter to open System Properties.
2. Switch to the Advanced tab and click Environment Variables.
3. Under System variables, click New:
   • Variable name: JAVA_HOME
   • Variable value: C:Program FilesEclipse Adoptiumjdk-21.0.x-hotspot (the folder path where JDK is installed).
4. Select the Path variable under System variables and click Edit.
5. Click New and add: %JAVA_HOME%in. Click OK on all windows.

Step 3: Verifying Java Installation in Terminal

Open a new Command Prompt (cmd) or PowerShell window and execute the following commands:

# Check Java Runtime version
java -version

# Output should resemble:
# openjdk version "21.0.2" 2024-01-16
# OpenJDK Runtime Environment Temurin-21.0.2+13 (build 21.0.2+13)
# OpenJDK 64-Bit Server VM Temurin-21.0.2+13 (build 21.0.2+13, mixed mode, sharing)

# Check Java Compiler version
javac -version
# Output: javac 21.0.2

Step 4: Compiling and Running via Command Line

Every developer should master manual terminal compilation before using an IDE:

# 1. Create a file named TestApp.java
# 2. Compile source code into bytecode (.class)
javac TestApp.java

# 3. Launch the bytecode on the JVM (omit the .class extension!)
java TestApp