Installation Guide - ashwani-cse/next-gen-pizza-backend GitHub Wiki

Installing and Switching Between JDK 17, JDK 21, and JDK 24 on macOS

Step 1: Check Installed JDK Versions

To list all installed JDK versions and their paths, run:

/usr/libexec/java_home -V

Expected output:

Matching Java Virtual Machines (4):
    24 (x86_64) "Oracle Corporation" - "OpenJDK 24" /Users/ashwanikumar/Library/Java/JavaVirtualMachines/jdk-24.jdk/Contents/Home
    21.0.6 (arm64) "Oracle Corporation" - "Java SE 21.0.6" /Library/Java/JavaVirtualMachines/jdk-21.jdk/Contents/Home
    17.0.10 (arm64) "Oracle Corporation" - "Java SE 17.0.10" /Library/Java/JavaVirtualMachines/jdk-17.jdk/Contents/Home
    17.0.10 (arm64) "Eclipse Adoptium" - "OpenJDK 17.0.10" /Users/ashwanikumar/Library/Java/JavaVirtualMachines/temurin-17.0.10/Contents/Home

This command is useful as some users extract JDK manually into /Users/ instead of /Library/Java/JavaVirtualMachines/.

Step 2: [Download JDK 24](https://jdk.java.net/)

Go to the official OpenJDK website:

🔗 [[Download JDK 24](https://jdk.java.net/)](https://jdk.java.net/)

Download the macOS x64 tar.gz file. It will be saved in the Downloads folder by default.

Step 3: Extract JDK 24

Move the downloaded JDK 24 tarball to a proper location and extract it.

mkdir -p ~/Library/Java/JavaVirtualMachines/jdk-24
mv ~/Downloads/openjdk-24_macos-x64_bin.tar.gz ~/Library/Java/JavaVirtualMachines/jdk-24/
cd ~/Library/Java/JavaVirtualMachines/jdk-24
tar -xzf openjdk-24_macos-x64_bin.tar.gz --strip-components=1

Verify Extraction

Check if the extracted folder exists:

ls ~/Library/Java/JavaVirtualMachines/

Expected output:

temurin-17.0.10
jdk-24

Find the extracted JDK 24 path:

ls ~/Library/Java/JavaVirtualMachines/jdk-24/

It should contain Contents/Home, so the JDK 24 path is:

/Users/ashwanikumar/Library/Java/JavaVirtualMachines/jdk-24/Contents/Home

Step 4: Set JDK 24 as Default

Ensure .zshrc exists before modifying it.

[ -f ~/.zshrc ] || touch ~/.zshrc
nano ~/.zshrc

Add the following lines:

export JAVA_HOME=$(/usr/libexec/java_home -v 24)
export PATH=$JAVA_HOME/bin:$PATH

Save and exit (Ctrl + X → Y → Enter).

Apply changes:

source ~/.zshrc

Verify:

java -version

Expected output:

openjdk 24 ...

Step 5: Easily Switch Between JDK 17, JDK 21 & JDK 24

Instead of editing .zshrc every time, add alias commands for switching.

nano ~/.zshrc

Add these lines at the end:

alias set_java17='export JAVA_HOME=$(/usr/libexec/java_home -v 17); export PATH=$JAVA_HOME/bin:$PATH; echo "Switched to Java 17: $JAVA_HOME"'
alias set_java21='export JAVA_HOME=$(/usr/libexec/java_home -v 21); export PATH=$JAVA_HOME/bin:$PATH; echo "Switched to Java 21: $JAVA_HOME"'
alias set_java24='export JAVA_HOME=$(/usr/libexec/java_home -v 24); export PATH=$JAVA_HOME/bin:$PATH; echo "Switched to Java 24: $JAVA_HOME"'

Save and exit (Ctrl + X → Y → Enter).

Apply changes:

source ~/.zshrc

Step 6: Switching Between JDK Versions

Switch to JDK 17:
```
set_java17
```
Switch to JDK 21:
```
set_java21
```
Switch to JDK 24:
```
set_java24
```

Verify the version:

java -version

✅ Final Setup Summary

✔ JDK 24 downloaded from [[[jdk.java.net](https://jdk.java.net/)](https://jdk.java.net/)
✔ JDK 24 installed from tar.gz
✔ JDK 24 set as default
✔ One-command switch between JDK 17, JDK 21 & JDK 24 using java_home

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