linux rhel8 安装java开发环境

[root@linuxprobe home]# cat /etc/system-release  ## 查看系统版本
Red Hat Enterprise Linux release 8.0 (Ootpa)
[root@linuxprobe home]# java    ##没有java命令
bash: java: command not found...
Failed to search for file: Cannot update read-only repo
[root@linuxprobe home]# java -version   ## 没有java版本信息
bash: java: command not found...
Failed to search for file: Cannot update read-only repo
[root@linuxprobe home]# which java   ##未安装java
/usr/bin/which: no java in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin)
[root@linuxprobe home]# rpm -qa | grep jdk   ## 没有java
[root@linuxprobe home]# echo $JAVA_HOME   ##没有java环境变量

[root@linuxprobe home]# uname -a   ## 查看内核架构
Linux linuxprobe.com 4.18.0-80.el8.x86_64 #1 SMP Wed Mar 13 12:02:46 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
[root@linuxprobe home]# hostnamectl  ## 查看内核架构
   Static hostname: linuxprobe.com
         Icon name: computer-vm
           Chassis: vm
        Machine ID: 1667052376ea4207aa566e9d7a42456b
           Boot ID: f05c4ad96bf5468a8f869ead700acc1a
    Virtualization: vmware
  Operating System: Red Hat Enterprise Linux 8.0 (Ootpa)
       CPE OS Name: cpe:/o:redhat:enterprise_linux:8.0:GA
            Kernel: Linux 4.18.0-80.el8.x86_64
      Architecture: x86-64

[root@linuxprobe local]# cd /usr/local  ## 安装包下载至此目录
[root@linuxprobe local]# ls
bin  etc  games  include  lib  lib64  libexec  sbin  share  src
[root@linuxprobe local]# ls  ## 在windows下载后上传，也可以直接在linux下载
bin  etc  games  include  jdk-15_linux-x64_bin.tar.gz  lib  lib64  libexec  sbin  share  src

[root@linuxprobe local]#tar -xzvf jdk-15_linux-x64_bin.tar.gz ##解压 
[root@linuxprobe local]# ls 
bin etc games include jdk-15 jdk-15_linux-x64_bin.tar.gz lib lib64 libexec sbin share src 
[root@linuxprobe local]# mv jdk-15_linux-x64_bin.tar.gz jdk-15  将安装移动至解压目录
[root@linuxprobe local]# mv jdk-15/ java  ## 重命名，方便配置环境变量

[root@linuxprobe local]# vim /etc/profile  ## vim 打开配置文件
G ## 打开后输入大写G进入末行
o ## 然后输入小写0，在下一行开始编辑，输入以下以export开头的四行（配置环境变量）
export JAVA_HOME=/usr/local/java
export PATH=$PATH:$JAVA_HOME/bin
export CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
export JRE_HOME=$JAVA_HOME/jre
source /etc/profile  ## 使环境变量生效

[root@linuxprobe local]# java  ## 直接在终端输入java 
Usage: java [options] <mainclass> [args...]
           (to execute a class)
   or  java [options] -jar <jarfile> [args...]
           (to execute a jar file)
   or  java [options] -m <module>[/<mainclass>] [args...]
       java [options] --module <module>[/<mainclass>] [args...]  …………………………
[root@linuxprobe local]# java -version  ## 可以查看到版本信息
java version "15" 2020-09-15
Java(TM) SE Runtime Environment (build 15+36-1562)
Java HotSpot(TM) 64-Bit Server VM (build 15+36-1562, mixed mode, sharing)
[root@linuxprobe local]# which java  ## 查找java命令
/usr/local/java/bin/java
[root@linuxprobe local]# rpm -qa | grep jdk  ## 没有使用rpm包安装，因此查询不到
[root@linuxprobe local]# echo $JAVA_HOME  ## 查询java环境变量
/usr/local/java