本文主要说明了在centos7系统下安装JDK8的详细步骤

• 1.1 下载jdk8
  下载jdk8

• 1.2 把下载好的jdk8包传输到centos7服务器

  
  
  image.png
• 1.3 解压
  tar -xvf jdk-8u241-linux-i586.tar.gz
  用ll命令查看解压后的文件

[root@iZipqoqa9axzz1Z java]# ll
total 190576
drwxr-xr-x 7 10143 10143      4096 Dec 11 18:52 jdk1.8.0_241
-rw-r--r-- 1 root  root  195143852 Mar 30 16:56 jdk-8u241-linux-i586.tar.gz
[root@iZipqoqa9axzz1Z java]# 

删除安装包rm -rf jdk-8u241-linux-i586.tar.gz(删除时输入 jdk-后，再按Tab键自动补全jdk安装包名字)
删除后查看目录：

[root@iZipqoqa9axzz1Z java]# ll
total 4
drwxr-xr-x 7 10143 10143 4096 Dec 11 18:52 jdk1.8.0_241

• 1.4 用vim编辑器设置jdk8的环境变量
  vim /etc/profile

# Path manipulation
if [ "$EUID" = "0" ]; then
    pathmunge /usr/sbin
    pathmunge /usr/local/sbin
else
    pathmunge /usr/local/sbin after
    pathmunge /usr/sbin after
fi

HOSTNAME=`/usr/bin/hostname 2>/dev/null`
HISTSIZE=1000
if [ "$HISTCONTROL" = "ignorespace" ] ; then
    export HISTCONTROL=ignoreboth
else
    export HISTCONTROL=ignoredups
fi

export PATH USER LOGNAME MAIL HOSTNAME HISTSIZE HISTCONTROL

# By default, we want umask to get set. This sets it for login shell
# Current threshold for system reserved uid/gids is 200
# You could check uidgid reservation validity in
# /usr/share/doc/setup-*/uidgid file
if [ $UID -gt 199 ] && [ "`/usr/bin/id -gn`" = "`/usr/bin/id -un`" ]; then
    umask 002
else
    umask 022
fi

for i in /etc/profile.d/*.sh /etc/profile.d/sh.local ; do
    if [ -r "$i" ]; then
        if [ "${-#*i}" != "$-" ]; then
            . "$i"
        else
            . "$i" >/dev/null
        fi
    fi
done

unset i
unset -f pathmunge

• 1,5 输入 i 键，切换到编辑模式（注：在最下方出现 --INSERT-- 才表示进入到编辑模式）

# Path manipulation
if [ "$EUID" = "0" ]; then
    pathmunge /usr/sbin
    pathmunge /usr/local/sbin
else
    pathmunge /usr/local/sbin after
    pathmunge /usr/sbin after
fi

HOSTNAME=`/usr/bin/hostname 2>/dev/null`
HISTSIZE=1000
if [ "$HISTCONTROL" = "ignorespace" ] ; then
    export HISTCONTROL=ignoreboth
else
    export HISTCONTROL=ignoredups
fi

export PATH USER LOGNAME MAIL HOSTNAME HISTSIZE HISTCONTROL

# By default, we want umask to get set. This sets it for login shell
# Current threshold for system reserved uid/gids is 200
# You could check uidgid reservation validity in
# /usr/share/doc/setup-*/uidgid file
if [ $UID -gt 199 ] && [ "`/usr/bin/id -gn`" = "`/usr/bin/id -un`" ]; then
    umask 002
else
    umask 022
fi

for i in /etc/profile.d/*.sh /etc/profile.d/sh.local ; do
    if [ -r "$i" ]; then
        if [ "${-#*i}" != "$-" ]; then
            . "$i"
        else
            . "$i" >/dev/null
        fi
    fi
done

unset i
unset -f pathmunge
-- INSERT --                                                                                                                                                                  78,1          Bot

移动光标在最下方填上：

JAVA_HOME=/fcj/java/jdk1.8.0_241

CLASSPATH=$JAVA_HOME/lib/

PATH=$PATH:$JAVA_HOME/bin

• 1.6 输入Esc 退出vim编辑模式，再按:wq+回车（保存并退出）
• 1.7 输入source /etc/profile使环境变量文件立即生效
• 1.8 用 java -version 命令查看JDK是否安装成功

[root@iZipqoqa9axzz1Z java]# java -version 
java version "1.8.0_241"
Java(TM) SE Runtime Environment (build 1.8.0_241-b07)
Java HotSpot(TM) Server VM (build 25.241-b07, mixed mode)
[root@iZipqoqa9axzz1Z java]#