MacOS 下切换Java JDK 版本

要查看已安装的版本，请使用：

/usr/libexec/java_home -V 

$ /usr/libexec/java_home -V
$ /usr/libexec/java_home -V
Matching Java Virtual Machines (4):
    14.0.2 (x86_64) "Oracle Corporation" - "Java SE 14.0.2" /Library/Java/JavaVirtualMachines/jdk-14.0.2.jdk/Contents/Home
    11.0.9 (x86_64) "GraalVM Community" - "GraalVM CE 20.3.0" /Library/Java/JavaVirtualMachines/graalvm-ce-java11-20.3.0/Contents/Home
    1.8.271.09 (x86_64) "Oracle Corporation" - "Java" /Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home
    1.8.0_265 (x86_64) "AdoptOpenJDK" - "AdoptOpenJDK 8" /Library/Java/JavaVirtualMachines/adoptopenjdk-8.jdk/Contents/Home
/Library/Java/JavaVirtualMachines/jdk-14.0.2.jdk/Contents/Home

然后只需在您~/.bashrc或~/.bash_profile：

alias java8='export JAVA_HOME=$(/usr/libexec/java_home -v 1.8.271.09)' 
alias openjdk8='export JAVA_HOME=$(/usr/libexec/java_home -v 1.8.0_265)' 
alias java11='export JAVA_HOME=$(/usr/libexec/java_home -v 11.0.9)' 
alias java14='export JAVA_HOME=$(/usr/libexec/java_home -v 14.0.2)' 

让脚本生效：

$ source ~/.bashrc

使用很简单，如

$ java11

就可以切换到java11

如果不嫌麻烦，也可以安装一个专门工具，如 jenv