1.从官网下载jdk-8u191-linux-x64.tar.gz，然后放在ubuntu里的Downloads文件夹里。然后解压到/usr/lib/jvm文件夹中。
sudo tar -zxvf Downloads/jdk-8u191-linux-x64.tar.gz -C /usr/lib/jvm
2.修改环境变量
sudo vim ~/.bashrc
修改jdk路径
export JAVA_HOME=/usr/lib/jvm/jdk1.8.0_191
3.设置系统默认jdk 版本
sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.8.0_191/bin/java 300 sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.8.0_191/bin/javac 300 sudo update-alternatives --install /usr/bin/jar jar /usr/lib/jvm/jdk1.8.0_191/bin/jar 300 sudo update-alternatives --install /usr/bin/javah javah /usr/lib/jvm/jdk1.8.0_191/bin/javah 300 sudo update-alternatives --install /usr/bin/javap javap /usr/lib/jvm/jdk1.8.0_191/bin/javap 300
执行
sudo update-alternatives --config java
成功：
原文：https://www.cnblogs.com/wl2017/p/9819984.html