How do I check if the Java JDK is installed on Mac?

Question

How do you check if Java SDK is installed on a Mac?

Is there a command line for this?

Answer 1

If you are on Mac OS Big Sur, then you probably have a messed up java installation. I found info on how to fix the issue with this article: https://knasmueller.net/how-to-install-java-openjdk-15-on-macos-big-sur

1. Download the .tar.gz file of the JDK on https://jdk.java.net/15/
2. Navigate to the download folder, and run these commands (move the .tar.gz file, extract it and remove it after extraction):

sudo mv openjdk-15.0.2_osx-x64_bin.tar.gz /Library/Java/JavaVirtualMachines/
cd /Library/Java/JavaVirtualMachines/
sudo tar -xzf openjdk-15.0.2_osx-x64_bin.tar.gz
sudo rm openjdk-15.0.2_osx-x64_bin.tar.gz

Note: it might be 15.0.3 or higher, depending on the date of your download.

3. run /usr/libexec/java_home -v15 and copy the output
4. add this line to your .bash_profile or .zshrc file, depending on which shell you are using. You will probably have only one of these files existing in your home directory (~/.bash_profile or ~/.zshrc).

JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk-15.0.2.jdk/Contents/Home

5. save the changes and make them effective right away by running: source ~/.bash_profile or source ~/.zshrc
6. check that java is working - run java -v