ubuntu14 安装jdk

1.下载JDK　　　

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

　　选择 jdk-8u101-linux-x64.tar.gz下载 

2. 解压缩

sudo tar -zxvf jdk-8u101-linux-x64.tar.gz -C /usr/lib/jvm

3.修改环境变量:　　

sudo vim ~/.bashrc

追加下面内容:

#set oracle jdk environment
export JAVA_HOME=/usr/lib/jvm/jdk1.8.0_101
export JRE_HOME=${JAVA_HOME}/jre
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
export PATH=$PATH:${JAVA_HOME}/bin

 环境变量生效

source ~/.bashrc

4.设置系统默认jdk 版本

sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.8.0_101/bin/java 300  
sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.8.0_101/bin/javac 300  
sudo update-alternatives --install /usr/bin/jar jar /usr/lib/jvm/jdk1.8.0_101/bin/jar 300   
sudo update-alternatives --install /usr/bin/javah javah /usr/lib/jvm/jdk1.8.0_101/bin/javah 300   
sudo update-alternatives --install /usr/bin/javap javap /usr/lib/jvm/jdk1.8.0_101/bin/javap 300 

　然后执行:

sudo update-alternatives --config java