查看“Jdk 多个版本行切换”的源代码

上传jdk7 和 jdk8 包
安装jdk1.7  和 jdk8
解压

 tar -zxvf /package/jdk-7u80-linux-x64.tar.gz
配置jdk变量
 vi /etc/profile
 export JAVA_HOME=/package/jdk1.7.0_80
 export CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
 export PATH=$PATH:$JAVA_HOME/bin

给jdk1.7 、1.8设置序列号

 alternatives --install /usr/bin/java java /package/jdk1.7.0_80 3
 alternatives --install /usr/bin/java java /package/jdk1.8.0_124 2
选择jdk对应的数字—切换jdk版本

 alternatives --config java
 There are 3 programs which provide 'java'.
  Selection    Command
 -----------------------------------------------
 *  1           /package/jdk1.8.0_121/java
   2           /package/jdk1.8.0_121/bin/java
 + 3           /package/jdk1.7.0_80/bin/java
 Enter to keep the current selection[+], or type selection number: 2