22.安装JDK

安装步骤

1. mkdir /opt/jdk
2. 通过xftp6上传到/opt/jdk下
3. cd /opt/jdk
4. 解压 tar -zxvf jdk-8u261-linux-x64.tar.gz
5. mkdir /usr/local/java
6. mv /opt/jdk/jdk1.8.0_261 /usr/local/java
7. 配置环境变量的配置文件vim /etc/profile
8. export JAVA_HOME=/usr/local/java/jdk1.8.0_261
9. export PATH=$JAVA_HOME/bin:$PATH
10. source /etc/profile 【让文件生效】

检测是否安装成功

编写Hello.java输出"hello, world!"