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

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

Is there a command line for this?

Make sure you correctly define the project's JDK and restart IntelliJ (full restart).

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

Just type javac. If it is installed you get usage information, otherwise it would just ask if you would like to install Java.

• Open terminal.

• run command to see:

  javac -version

• Also you can verify manually by going to the specific location and then check. To do this run below command in the mac terminal

  cd /Library/Java/JavaVirtualMachines/

Then run ls command in the terminal again. Now you can see the jdk version & package if exists in your computer.

Type in a terminal:

which javac

It should show you something like

/usr/bin/javac

You can leverage the java_home helper binary on OS X for what you're looking for.

To list all versions of installed JDK:

$ /usr/libexec/java_home -V
Matching Java Virtual Machines (2):
    1.8.0_51, x86_64:   "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_51.jdk/Contents/Home
    1.7.0_79, x86_64:   "Java SE 7" /Library/Java/JavaVirtualMachines/jdk1.7.0_79.jdk/Contents/Home

To request the JAVA_HOME path of a specific JDK version, you can do:

$ /usr/libexec/java_home -v 1.7
/Library/Java/JavaVirtualMachines/jdk1.7.0_79.jdk/Contents/Home

$ /usr/libexec/java_home -v 1.8
/Library/Java/JavaVirtualMachines/jdk1.8.0_51.jdk/Contents/Home

You could take advantage of the above commands in your script like this:

REQUESTED_JAVA_VERSION="1.7"
if POSSIBLE_JAVA_HOME="$(/usr/libexec/java_home -v $REQUESTED_JAVA_VERSION 2>/dev/null)"; then
    # Do this if you want to export JAVA_HOME
    export JAVA_HOME="$POSSIBLE_JAVA_HOME"
    echo "Java SDK is installed"
else
    echo "Did not find any installed JDK for version $REQUESTED_JAVA_VERSION"
fi

You might be able to do if-else and check for multiple different versions of java as well.

If you prefer XML output, java_home also has a -X option to output in XML.

$ /usr/libexec/java_home --help
Usage: java_home [options...]
    Returns the path to a Java home directory from the current user's settings.

Options:
    [-v/--version   <version>]       Filter Java versions in the "JVMVersion" form 1.X(+ or *).
    [-a/--arch      <architecture>]  Filter JVMs matching architecture (i386, x86_64, etc).
    [-d/--datamodel <datamodel>]     Filter JVMs capable of -d32 or -d64
    [-t/--task      <task>]          Use the JVM list for a specific task (Applets, WebStart, BundledApp, JNI, or CommandLine)
    [-F/--failfast]                  Fail when filters return no JVMs, do not continue with default.
    [   --exec      <command> ...]   Execute the $JAVA_HOME/bin/<command> with the remaining arguments.
    [-R/--request]                   Request installation of a Java Runtime if not installed.
    [-X/--xml]                       Print full JVM list and additional data as XML plist.
    [-V/--verbose]                   Print full JVM list with architectures.
    [-h/--help]                      This usage information.

/usr/bin/java_home tool returns 1 if java not installed.

So you can check if java is installed by the next way:

/usr/libexec/java_home &> /dev/null && echo "installed" || echo  "not installed"

Below command worked out pretty good:

javac -version

I also manually verified by navigating to the Java Folder on my Mac

/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk