Ubuntu 16.04 LTS安装配置openjdk-7-jdk

注：ubuntu16.04默认没有openjdk-7-jdk的安装源，必须另外添加。

# add-apt-repository ppa:openjdk-r/ppa
# apt-get update
# apt-cache search openjdk
# apt-get install openjdk-7-jdk

# update-alternatives --config java  #版本切换命令
# update-alternatives --config javac

# 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-8-openjdk-amd64/jre/bin/java   1081      auto mode
  1            /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java   1071      manual mode
  2            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1081      manual mode

Press <enter> to keep the current choice[*], or type selection number: 1
update-alternatives: using /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java to provide /usr/bin/java (java) in manual mode

# update-alternatives --config javac
There are 2 choices for the alternative javac (providing /usr/bin/javac).

  Selection    Path                                         Priority   Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-8-openjdk-amd64/bin/javac   1081      auto mode
  1            /usr/lib/jvm/java-7-openjdk-amd64/bin/javac   1071      manual mode
  2            /usr/lib/jvm/java-8-openjdk-amd64/bin/javac   1081      manual mode

Press <enter> to keep the current choice[*], or type selection number: 1
update-alternatives: using /usr/lib/jvm/java-7-openjdk-amd64/bin/javac to provide /usr/bin/javac (javac) in manual mode

# java -version
java version "1.7.0_95"
OpenJDK Runtime Environment (IcedTea 2.6.4) (7u95-2.6.4-3)
OpenJDK 64-Bit Server VM (build 24.95-b01, mixed mode)