ubuntu 安装 java JDK

1. oracle 官网下载最新版本的Java JDK (www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html)

2. 解压缩下载文件，复制文件到usr/lib/jdk下(cp -r ~/Downloads/jdk1.8.0_65/ /usr/lib/jdk)

3. 编辑 /etc/profile 文件 (sudo gedit /etc/profile)

4. 添加到文件最后并保存

export JAVA_HOME=/usr/lib/jdk/jdk1.8.0_65
export JRE_HOME=/usr/lib/jdk/jdk1.8.0_65/jre
export PATH=$JAVA_HOME/bin:$JAVA_HOME/jre/bin:$PATH
export CLASSPATH=$CLASSPATH:.:$JAVA_HOME/lib:$JAVA_HOME/jre/lib

5. 更新系统默认jdk

sudo update-alternatives --install /usr/bin/java java /usr/lib/jdk/jdk1.8.0_65/bin/java 300
sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jdk/jdk1.8.0_65/bin/javac 300
sudo update-alternatives --config java
sudo update-alternatives --config javac

6. 检查java版本 (java -version)