JAVA JDK版本切换

首先安装sun1.6，这里我安装的目录是/usr/java/jdk1.6.0_45

然后设置profile文件/etc/profile(文件的末尾添加该文件)

sudo vim /etc/profile

export JAVA_HOME=/usr/java/jdk1.6.0_45
export JRE_HOME=/usr/java/jdk1.6.0_45/jre
export CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
export PATH=$PATH:$JAVA_HOME/bin

source /etc/profile

然后安装openjdk1.7，在software center中可以进行安装，安装完毕后执行如下命令：

gsc@gsc-250:~$ sudo update-alternatives --install /usr/bin/java java /usr/java/jdk1.6.0_45/bin/java 300
gsc@gsc-250:~$ sudo update-alternatives --install /usr/bin/javac javac /usr/java/jdk1.6.0_45/bin/javac 300
gsc@gsc-250:~$ sudo update-alternatives --install /usr/bin/javadoc javadoc /usr/java/jdk1.6.0_45/bin/javadoc 300
gsc@gsc-250:~$ sudo update-alternatives --install /usr/bin/javap javap /usr/java/jdk1.6.0_45/bin/javap 300

使用如下命令切换：

gsc@gsc-250:~/my_carreer/webrtc-checkout$ sudo update-alternatives --config java
There are 2 choices for the alternative java (providing /usr/bin/java).

Selection    Path                                            Priority   Status
------------------------------------------------------------
0            /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java   1071      auto mode
1            /usr/java/jdk1.6.0_45/bin/java                   300       manual mode
* 2            /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java   1071      manual mode

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

查看当前java版本：
<pre name="code" class="html">gsc@gsc-250:~/my_carreer/webrtc-checkout$ java -version
java version "1.7.0_85"
OpenJDK Runtime Environment (IcedTea 2.6.1) (7u85-2.6.1-5ubuntu0.14.04.1)
OpenJDK 64-Bit Server VM (build 24.85-b03, mixed mode)