How can I change Mac OS's default Java VM returned from /usr/libexec/java_home

Question

(Wasn\'t sure if this should go on SU... migration is certainly an option, but more programmers read questions here, so here goes).

I am running Mac OS X 10.8.4, and

Answer 1

MacOS uses /usr/libexec/java_home to find the current Java Version. One way to bypass is to change the plist file as explained by @void256 above. Other ways is to take the backup of the java_home and replace it with your own script java_home having the code
echo $JAVA_HOME

Now export the JAVA_HOME to the desired version of the SDK by adding the following commands to the ~/.bash_profile. export JAVA_HOME="/System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home" launchctl setenv JAVA_HOME $JAVA_HOME /// Make the environment variable global

Run the command source ~/.bash_profile to the run the above commands.

Anytime one needs to change the JAVA_HOME he can reset the JAVA_HOME value in the ~/.bash_profile file.

Answer 2

I wanted to change default java version form 1.6* to 1.7*. I tried the following steps and it worked for me:

• Removed link "java" from under /usr/bin
• Created it again, pointing to the new location:

ln -s /Library/Java/JavaVirtualMachines/jdk1.7.0_51.jdk/Contents/Home/bin/java java

• verified with "java -version"

java version "1.7.0_51"
Java(TM) SE Runtime Environment (build 1.7.0_51-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.51-b03, mixed mode)

Answer 3

I actually looked at this a little in the disassembler, since source isn't available.

/usr/bin/java and /usr/libexec/java_home both make use of JavaLaunching.framework. The JAVA_HOME environment variable is indeed checked first by /usr/bin/java and friends (but not /usr/libexec/java_home.) The framework uses the JAVA_VERSION and JAVA_ARCH envirionment variables to filter the available JVMs. So, by default:

$ /usr/libexec/java_home -V
Matching Java Virtual Machines (2):
    11.0.5, x86_64: "Amazon Corretto 11"    /Library/Java/JavaVirtualMachines/amazon-corretto-11.jdk/Contents/Home
    1.8.0_232, x86_64:  "Amazon Corretto 8" /Library/Java/JavaVirtualMachines/amazon-corretto-8.jdk/Contents/Home

/Library/Java/JavaVirtualMachines/amazon-corretto-11.jdk/Contents/Home

But setting, say, JAVA_VERSION can override the default:

$ JAVA_VERSION=1.8 /usr/libexec/java_home
/Library/Java/JavaVirtualMachines/amazon-corretto-8.jdk/Contents/Home

You can also set JAVA_LAUNCHER_VERBOSE=1 to see some additional debug logging as far as search paths, found JVMs, etc., with both /usr/bin/java and /usr/libexec/java_home.

In the past, JavaLaunching.framework actually used the preferences system (under the com.apple.java.JavaPreferences domain) to set the preferred JVM order, allowing the default JVM to be set with PlistBuddy - but as best as I can tell, that code has been removed in recent versions of macOS. Environment variables seem to be the only way (aside from editing the Info.plist in the JDK bundles themselves.)

Setting default environment variables can of course be done through your .profile or via launchd, if you need them be set at a session level.

Answer 4

It's actually pretty easy. Let's say we have this in our JavaVirtualMachines folder:

• jdk1.7.0_51.jdk
• jdk1.8.0.jdk

Imagine that 1.8 is our default, then we just add a new folder (for example 'old') and move the default jdk folder to that new folder. Do java -version again et voila, 1.7!

Answer 5

Edit: this information is for visualvm specifically, not for any other java app

As mentioned by others, you need to modify the visualvm.conf

For the latest version of JvisualVM 1.3.6 on Mac, the install directories have changed.

It is currently in /Applications/VisualVM.app/Contents/Resources/visualvm/etc/visualvm.conf.

However this may depend on where you have installed VisualVM. The easiest way to find where your VisualVM is to start it, and then look at the process using:

ps -ef | grep VisualVM

You will see something like:

... -Dnetbeans.dirs=/Applications/VisualVM.app/Contents/Resources/visualvm/visualvm...

You want to take the netbeans.dir property and look up a directory and you will find the etc folder.

Uncomment this line in the visualvm.conf and change the path to the jdk

visualvm_jdkhome="/path/to/jdk"

Additionally, if you are having slowness with your visualvm and you have a lot of memory, I would suggest greatly increasing the amount of memory available and running it in server mode:

visualvm_default_options="-J-XX:MaxPermSize=96m -J-Xmx2048m -J-Xms2048m -J-server -J-XX:+UseCompressedOops -J-XX:+UseConcMarkSweepGC -J-XX:+UseParNewGC -J-XX:NewRatio=2 -J-Dnetbeans.accept_license_class=com.sun.tools.visualvm.modules.startup.AcceptLicense -J-Dsun.jvmstat.perdata.syncWaitMs=10000 -J-Dsun.java2d.noddraw=true -J-Dsun.java2d.d3d=false"

Answer 6

Oracle's uninstallation instructions for Java 7 worked for me.

Excerpt:

Uninstalling the JDK To uninstall the JDK, you must have Administrator privileges and execute the remove command either as root or by using the sudo(8) tool.

Navigate to /Library/Java/JavaVirtualMachines and remove the directory whose name matches the following format:*

/Library/Java/JavaVirtualMachines/jdk<major>.<minor>.<macro[_update]>.jdk

For example, to uninstall 7u6:

% rm -rf jdk1.7.0_06.jdk