命令行一键切换java版本的几种方式

序

本文主要讲述一下命令行一键切换java版本的几种方式

背景

java现在版本发布相对以前比较频繁了，java9还没来得及用，java10就出来了，2018年9月份java11也要来了，于是就有需求在笔记本电脑上装多个版本的java，一键切换就变得极为迫切。

zsh function实现

~/.zshrc

function jvm {
    version=$1
    case "$version" in
    9)
        export JAVA_HOME='/Library/Java/JavaVirtualMachines/jdk-9.jdk/Contents/Home'
        ;;
    10)
        export JAVA_HOME='/Library/Java/JavaVirtualMachines/jdk-10.jdk/Contents/Home'
        ;;
    *)
        export JAVA_HOME='/Library/Java/JavaVirtualMachines/jdk1.8.0_151.jdk/Contents/Home'
        ;;
    esac     
}

值得注意的是这个命令只对当前命令窗口有效。新开的窗口还是使用~/.zshrc里头原来配置的JAVA_HOME版本。

使用实例

jvm 8
java -version
java version "1.8.0_151"
Java(TM) SE Runtime Environment (build 1.8.0_151-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.151-b12, mixed mode)

jvm 9
java -version
java version "9"
Java(TM) SE Runtime Environment (build 9+181)
Java HotSpot(TM) 64-Bit Server VM (build 9+181, mixed mode)

jvm10
java -version
openjdk version "10" 2018-03-20
OpenJDK Runtime Environment 18.3 (build 10+46)
OpenJDK 64-Bit Server VM 18.3 (build 10+46, mixed mode)

jenv

jenv有点类似node的nvm之类的用来管理多版本

安装

brew install jenv
echo 'export PATH="$HOME/.jenv/bin:$PATH"' >> ~/.zshrc
echo 'eval "$(jenv init -)"' >> ~/.zshrc
mkdir -p  ~/.jenv/versions

注册java版本

jenv add /Library/Java/JavaVirtualMachines/jdk1.8.0_151.jdk/Contents/Home
jenv add /Library/Java/JavaVirtualMachines/jdk-9.jdk/Contents/Home
jenv add /Library/Java/JavaVirtualMachines/jdk-10.jdk/Contents/Home

查看版本

jenv versions
* system (set by /Users/demo/.jenv/version)
  1.8
  1.8.0.151
  10
  9
  openjdk64-10
  oracle64-1.8.0.151
  oracle64-9

切换

➜  ~ jenv local 1.8
➜  ~ java -version
java version "1.8.0_151"
Java(TM) SE Runtime Environment (build 1.8.0_151-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.151-b12, mixed mode)

➜  ~ jenv local 9
➜  ~ java -version
java version "9"
Java(TM) SE Runtime Environment (build 9+181)
Java HotSpot(TM) 64-Bit Server VM (build 9+181, mixed mode)

➜  ~ jenv local 10
➜  ~ java -version
openjdk version "10" 2018-03-20
OpenJDK Runtime Environment 18.3 (build 10+46)
OpenJDK 64-Bit Server VM 18.3 (build 10+46, mixed mode)