linux多版本jdk切换

$ alternatives --display java

$ sudo alternatives --install /usr/bin/java java /opt/jdk1.7.0_80/bin/java 1  
$ sudo alternatives --install /usr/bin/javac javac /opt/jdk1.7.0_80/bin/javac 1  
$ sudo alternatives --install /usr/bin/jar jar /opt/jdk1.7.0_80/bin/jar 1

$ alternatives --config java

There are 2 programs which provide 'java'.

  Selection    Command
-----------------------------------------------
*+ 1           java-1.8.0-openjdk.x86_64 (/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.131-3.b12.el7_3.x86_64/jre/bin/java)
   2           /opt/jdk1.7.0_80/bin/java

Enter to keep the current selection[+], or type selection number:2

$ java -version
java version "1.7.0_80"
Java(TM) SE Runtime Environment (build 1.7.0_80-b15)
Java HotSpot(TM) 64-Bit Server VM (build 24.80-b11, mixed mode)