01 how to install the JDK on Windows

Step 1: Download the JDK
Go to the official source: Visit Oracle's Java download page or Eclipse Adoptium for OpenJDK builds.
Select your version: Choose a recent version like JDK 21 (LTS) or newer, ensuring you pick the Windows x64 installer (usually an .exe file).
Accept license: Agree to the license terms if prompted (especially for Oracle).
Step 2: Run the Installer
Locate the file: Find the downloaded .exe file (e.g., jdk-21_windows-x64_bin.exe).
Start installation: Double-click the file to launch the installer wizard.
Follow prompts: Click "Next" and keep the default installation path (e.g., C:\Program Files\Java\jdk-21) unless you have a reason to change it.
Step 3: Set Environment Variables (Crucial)
Find the JDK path: Navigate to the bin folder inside your installed JDK directory (e.g., C:\Program Files\Java\jdk-21\bin), and copy this path.
Open System Properties: Search for "Edit the system environment variables" in the Start Menu and open it, then click "Environment Variables".
Edit Path: Under "System variables," find and edit the Path variable. Click "New" and paste the copied bin folder path.
Create JAVA_HOME: Click "New" again. Set Variable name to JAVA_HOME and Variable value to the root JDK path (e.g., C:\Program Files\Java\jdk-21, without the \bin).
Confirm: Click OK on all windows to save changes.
Step 4: Verify Installation
Open Command Prompt: Close and reopen any Command Prompt (cmd) windows.
Check Java: Type java -version and press Enter. You should see the installed Java version.
Check Compiler: Type javac -version and press Enter to confirm the compiler is working.
Check JAVA_HOME: Type echo %JAVA_HOME% and press Enter to see if the variable is set correctly.