Mac OS Java家庭歧义

Question

Please see these 3 commands and their outcomes in MacOS:

Korays-MacBook-Pro:~ koraytugay$ /usr/libexec/java_home
/Library/Java/JavaVirtualMachines/jdk1.8.0_11.jdk/Contents/Home

Korays-MacBook-Pro:~ koraytugay$ java -version
java version "1.7.0_55"
Java(TM) SE Runtime Environment (build 1.7.0_55-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.55-b03, mixed mode)

Korays-MacBook-Pro:~ koraytugay$ echo $JAVA_HOME
/Library/Java/JavaVirtualMachines/jdk1.7.0_55.jdk/Contents/Home

Why does the first one return 1.8? What exactly is /libexec/java_home ?

Answer 1

Koray,

As per the Oracle docs ...

JAVA_HOME is just an environment variable used to trigger the 'java' found in your PATH to use a different JDK image. Unfortunately, not all 'java' startup scripts obey this env variable. It's also used by many java tool startup scripts to determine what 'java' to run, bypassing the 'java' found in the PATH setting. Setting this variable during a JDK build is a bad idea, don't do it.

I use Eclipse myself, and don't have a JAVA_HOME env variable defined, here is my output running the same commands.

brandon@brandons-mbp ~
$ /usr/libexec/java_home 
/Library/Java/JavaVirtualMachines/jdk1.8.0_05.jdk/Contents/Home

brandon@brandons-mbp ~
$ java -version
java version "1.8.0_05"
Java(TM) SE Runtime Environment (build 1.8.0_05-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.5-b02, mixed mode)

brandon@brandons-mbp ~
$ echo $JAVA_HOME

Not sure why you have two different versions but did you try updating your JDK recently? Maybe when you upgraded it failed to launch a script to update your $JAVA_HOME.

Here's the instructions for installing JDK and setting JAVA_HOME on *nix based OSes.

Let me know if that helps I can help you dig deeper if need be.