debian-7.11.0-amd64安装Oracle官方的jdk1.8

原系统中安装的是java-6-openjdk-amd64

java -version

java version "1.6.0_38"
OpenJDK Runtime Environment (IcedTea6 1.13.10) (6b38-1.13.10-1~deb7u1)
OpenJDK 64-Bit Server VM (build 23.25-b01, mixed mode)

而tika 1.11要求java 1.7，但1.7似乎Oracle不提供下载了，转而安装1.8

http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html

下载文件为

jdk-8u181-linux-x64.tar.gz

解压到

/usr/lib/jvm/jdk1.8.0_181

joe /etc/profile添加环境变量

export JAVA_HOME=/usr/lib/jdk1.8.0_181
export JRE_HOME=${JAVA_HOME}/jre
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
export PATH=${JAVA_HOME}/bin:$PATH

重启让环境生效，开始建立链接.加入到系统的/usr/bin，用update-alternatives命令来维护系统的软连接，通过更新这个来让系统知道用哪个命令，最后一个参数是优先级，越高越好。

#update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.8.0_181/bin/java 1100
#update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.8.0_181/bin/javac 1100

# update-alternatives --config java
There are 2 choices for the alternative java (providing /usr/bin/java).
 
  Selection    Path                                            Priority   Status
------------------------------------------------------------
  0            /usr/lib/jvm/jdk1.8.0_181/bin/java               1100      auto mode
* 1            /usr/lib/jvm/jdk1.8.0_181/bin/java               1100      manual mode
  2            /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java   1061      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/jdk1.8.0_181/bin/javac           1100      auto mode
  1            /usr/lib/jvm/jdk1.8.0_181/bin/javac           1100      manual mode
  2            /usr/lib/jvm/java-6-openjdk-amd64/bin/javac   1061      manual mode

 java -version

java version "1.8.0_181"
Java(TM) SE Runtime Environment (build 1.8.0_181-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.181-b13, mixed mode)