安装Ubuntu时，默认安装了OpenJDK_1.7

$ java -version

java version "1.7.0_79"

OpenJDK Runtime Environment (IcedTea 2.5.6) (7u79-2.5.6-0ubuntu1.12.04.1)

OpenJDK 64-Bit Server VM (build 24.79-b02, mixed mode)

现在需要安装JDK_1.6

安装在/opt/java/jdk1.6.0_45

/opt/java/jdk1.6.0_45# ls

bin        db       jre  LICENSE  README.html  THIRDPARTYLICENSEREADME.txt

COPYRIGHT  include  lib  man      src.zip

加上环境变量

用户环境变量：~/.bashrc中增加行

export JAVA_HOME=/opt/java/jdk1.6.0_45

export JRE_HOME=$JAVA_HOME/jre

export CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JRE_HOME/lib/tools.jar

export PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin

export USE_CCACHE=1

系统环境变量：/etc/profile中增加行

export JAVA_HOME=/opt/java/jdk1.6.0_45

export JRE_HOME=$JAVA_HOME/jre

export CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JRE_HOME/lib/tools.jar

export PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin

export USE_CCACHE=1

通过update-alternatives切换软件版本

增加JDK_1.6的命令连接符，使用--install选项

$ sudo update-alternatives --install /usr/bin/java java /opt/java/jdk1.6.0_45/bin/java 1062  

如需移除，--remove选项

$ sudo update-alternatives --remove /usr/bin/java java /opt/java/jdk1.6.0_45/bin/java 1062

创建默认命令链接 --config

$ sudo update-alternatives --config java

There are 2 choices for the alternative java (providing /usr/bin/java).

  Selection    Path                   Priority  Status

------------------------------------------------------------------------------------

* 0    /opt/java/jdk1.6.0_45/bin/java            1062      auto mode

 1    /opt/java/jdk1.6.0_45/bin/java            1062      manual mode

 2    /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java   1051      manual mode

Press enter to keep the current choice[*], or type selection number:0

同理Python也可以这样切换

本文出自 “M层” 博客，请务必保留此出处http://mengix.blog.51cto.com/7194660/1860961

Ubuntu下切换多个JDK环境