1.官网下载JDK

地址: https://www.oracle.com/java/technologies/downloads/

选择相应的 .gz包下载

2.解压缩,放到指定目录

创建目录:

sudo mkdir /usr/lib/jvm

解压缩到该目录:

sudo tar -zxvf jdk-8u381-linux-x64.tar.gz -C /usr/lib/jvm

3.配置环境变量

sudo vim ~/.bashrc

文件的末尾追加下面内容:

#set oracle jdk environment
export JAVA_HOME=/usr/lib/jvm/jdk1.8.0_381  ## 这里要注意目录要换成自己解压的jdk 目录
export JRE_HOME=${JAVA_HOME}/jre  
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib  
export PATH=${JAVA_HOME}/bin:$PATH

使环境变量马上生效

source ~/.bashrc

4.设置系统默认JDK

sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.8.0_381/bin/java 300  
sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.8.0_381/bin/javac 300  
sudo update-alternatives --install /usr/bin/jar jar /usr/lib/jvm/jdk1.8.0_381/bin/jar 300   
sudo update-alternatives --install /usr/bin/javah javah /usr/lib/jvm/jdk1.8.0_381/bin/javah 300   
sudo update-alternatives --install /usr/bin/javap javap /usr/lib/jvm/jdk1.8.0_381/bin/javap 300

然后执行:

sudo update-alternatives --config java

若是初次安装jdk,会有下面的提示

There is only one alternative in link group java (providing /usr/bin/java): /usr/lib/jvm/jdk1.8.0_381/bin/java

否者,选择合适的jdk

5. 测试jdk

java -version