打开终端，输入：/usr/libexec/java_home -V
注意：输入命令参数区分大小写(-v是不对的，必须是-V)
如下图2个红框内依次为：当前Mac已安装jdk目录； Mac默认使用的jdk版本；
Matching Java Virtual Machines (2):
1.8.281.09 (x86_64) "Oracle Corporation" - "Java" /Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home
1.8.0_201 (x86_64) "Oracle Corporation" - "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home
/Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home