ubuntu 中配置java环境（本地安装包）

1、查看系统位数、系统内核

root@ubuntu02:/home# getconf LONG_BIT
64

root@ubuntu02:/home# 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、查看当前java环境

root@ubuntu02:~# java -version   //忽略提示，使用安装包进行安装

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、官网下载最新java jdk安装包

下载地址：https://www.oracle.com/java/technologies/downloads/#java8

root@ubuntu02:/home/software# wget https://download.oracle.com/otn/java/jdk/8u311-b11/4d5417147a92418ea8b615e228bb6935/jdk-8u311-linux-x64.tar.gz

root@ubuntu02:/home/software# tar -xzvf jdk-8u311-linux-x64.tar.gz

root@ubuntu02:/home/software# ls
jdk1.8.0_311  jdk-8u311-linux-x64.tar.gz

4、创建安装目录

root@ubuntu02:/home/software# mkdir -p /usr/lib/jdk
root@ubuntu02:/home/software# mv jdk1.8.0_311 /usr/lib/jdk   //移动至指定目录

5、配置java环境变量

root@ubuntu02:/home/software# vim /etc/profile

#java env
export JAVA_HOME=/usr/lib/jdk/jdk1.8.0_311
export JRE_HOME=${JAVA_HOME}/jre    
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib    
export PATH=${JAVA_HOME}/bin:$PATH

6、立即生效

root@ubuntu02:/home/software# source /etc/profile

7、配置软连接：

root@ubuntu02:/home/software# update-alternatives --install /usr/bin/java  java  /usr/lib/jdk/jdk1.8.0_311/bin/java 300
update-alternatives: using /usr/lib/jdk/jdk1.8.0_311/bin/java to provide /usr/bin/java (java) in auto mode
root@ubuntu02:/home/software# update-alternatives --install /usr/bin/javac  javac  /usr/lib/jdk/jdk1.8.0_311/bin/javac 300
update-alternatives: using /usr/lib/jdk/jdk1.8.0_311/bin/javac to provide /usr/bin/javac (javac) in auto mode

8、测试安装效果

root@ubuntu02:/home/software# java -version
java version "1.8.0_311"
Java(TM) SE Runtime Environment (build 1.8.0_311-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.311-b11, mixed mode)

参考：https://www.cnblogs.com/lfri/p/10437266.html