1、核心版本

root@ubuntu02:~# hostnamectl
   Static hostname: ubuntu02
         Icon name: computer-vm
           Chassis: vm
        Machine ID: 3c186d21e7094b71a8889a2d78350c4b
           Boot ID: cc8cf35b8ad54b68a5a2f07eb4042153
    Virtualization: vmware
  Operating System: Ubuntu 20.04.3 LTS
            Kernel: Linux 
 
5.11.0-38-generic
      Architecture: x86-64

2、測試java

root@ubuntu02:~# java

Command 'java' not found, but can be installed with:

apt install openjdk-11-jre-headless  # version 11.0.11+9-0ubuntu2~20.04, or
apt install default-jre              # version 2:1.11-72
apt install openjdk-13-jre-headless  # version 13.0
 
.7+5-0ubuntu1~20.04
apt install openjdk-16-jre-headless  # version 16.0.1+9-1~20.04
apt install openjdk-17-jre-headless  # version 17+35-1~20.04
apt install openjdk-8-jre-headless   # version 8u292-b10-0ubuntu1~20.04

root@ubuntu02:~# java --version

Command 'java' not found, but can be installed with:

apt install openjdk
 
-11-jre-headless  # version 11.0.11+9-0ubuntu2~20.04, or
apt install default-jre              # version 2:1.11-72
apt install openjdk-13-jre-headless  # version 13.0.7+5-0ubuntu1~20.04
apt install openjdk-16-jre-headless  # version 16.0.1+9-1~20.04
apt install openjdk-17-jre-headless  # version 17+35-1~20.04
apt install openjdk-8-jre-headless   # version 8u292-b10-0ubuntu1~20.04

3、直接安裝

root@ubuntu02:~# apt install openjdk-11-jre-headless
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
  ca-certificates-java java-common
Suggested packages:
  default-jre fonts-dejavu-extra fonts-ipafont-gothic fonts-ipafont-mincho fonts-wqy-microhei | fonts-wqy-zenhei
The following NEW packages will be installed:
…………
Updating certificates in /etc/ssl/certs...
0 added, 0 removed; done.
Running hooks in /etc/ca-certificates/update.d...

done.
done.

4、測試效果

root@ubuntu02:~# java -v  // ？？？？？
Unrecognized option: -v
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.
root@ubuntu02:~# java --version
openjdk 11.0.11 2021-04-20
OpenJDK Runtime Environment (build 11.0.11+9-Ubuntu-0ubuntu2.20.04)
OpenJDK 64-Bit Server VM (build 11.0.11+9-Ubuntu-0ubuntu2.20.04, mixed mode, sharing)
root@ubuntu02:~#