Ubuntu16.04安装jdk1.8

下载JDK1.8的源码：

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


#新建目录

mkdir /usr/java#解压
tar -zxvf jdk-8u111-linux-x64.tar.gz -C /usr/java#配置环境变量
vim ~/.bashrc#在末尾添加
#java env
export JAVA_HOME=/usr/java/jdk1.8.0_111
export JRE_HOME=${JAVA_HOME}/jre
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
export PATH=$PATH:${JAVA_HOME}/bin
#立即生效
source ~/.bashrc#测试
java -version#输出
java version "1.8.0_111"
Java(TM) SE Runtime Environment (build 1.8.0_111-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.111-b14, mixed mode)#如果安装了多个JDK版本，可配置JDK版本
update-alternatives --install /usr/bin/java java /usr/java/jdk1.8.0_111/bin/java 8111
update-alternatives --install /usr/bin/javac javac /usr/java/jdk1.8.0_111/bin/javac 8111
update-alternatives --install /usr/bin/jar jar /usr/java/jdk1.8.0_111/bin/jar 8111
update-alternatives --install /usr/bin/javah javah /usr/java/jdk1.8.0_111/bin/javah 8111
update-alternatives --install /usr/bin/javap javap /usr/java/jdk1.8.0_111/bin/javap 8111#查看和删除
update-alternatives --display java
update-alternatives --remove java /usr/java/jdk1.8.0_111/bin/java# config
update-alternatives --config java#初次安装，会提示没有选项，否则会有选项可选
root@ubuntu:/# update-alternatives --config java
There is only one alternative in link group java (providing /usr/bin/java): /usr/java/jdk1.8.0_111/bin/java
Nothing to configure.