设置Mac系统的JAVA_HOME环境变量:

打开终端
编辑 ~/.bash_profile
新增一行内容 export JAVA_HOME=$(/usr/libexec/java_home)
执行 source .bash_profile
测试: echo $JAVA_HOME

in this tutorial, we show you how to set $JAVA_HOME environment variable on latest or older Mac OSX.

1. Mac OSX 10.5 or later
   In Mac OSX 10.5 or later, Apple recommends to set the $JAVA_HOME variable to /usr/libexec/java_home, just export $JAVA_HOME in file ~/.bash_profile or ~/.profile.

vim .bash_profile
    export JAVA_HOME=$(/usr/libexec/java_home)
source .bash_profile
echo $JAVA_HOME
    /Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home

Why /usr/libexec/java_home?
This java_home can return the Java version specified in Java Preferences for the current user. For examples,

/usr/libexec/java_home -V
    Matching Java Virtual Machines (3):
    1.7.0_05, x86_64:   "Java SE 7" /Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home
    1.6.0_41-b02-445, x86_64:   "Java SE 6" /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home
    1.6.0_41-b02-445, i386: "Java SE 6" /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home

This Mac OSX has three JDK installed.

##return top Java version
$ /usr/libexec/java_home
    /Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home

## I want Java version 1.6
$ /usr/libexec/java_home -v 1.6
    /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home

Ref: https://www.mkyong.com/java/how-to-set-java_home-environment-variable-on-mac-os-x/

参考：

https://blog.alanwei.com/blog/2021/03/03/mac-java-home/