文章目录
下载JDK
下载页面：戳这里 Java SE Download
如果需要历史版本，拖到页面最下方 Java Archive
可以看到 
官网上提供的两种格式
安装 rpm格式的 JDK
rpm 类似windows 操作系统上的 exe执行文件， 默认安装到 /usr/java目录下
Step1 rpm -ivh 安装
[root@artisan soft_artisan]# rpm -ivh jdk-8u221-linux-x64.rpm
warning: jdk-8u221-linux-x64.rpm: Header V3 RSA/SHA256 Signature, key ID ec551f03: NOKEY
Preparing... ################################# [100%]
Updating / installing...
1:jdk1.8-2000:1.8.0_221-fcs ################################# [100%]
Unpacking JAR files...
tools.jar...
plugin.jar...
javaws.jar...
deploy.jar...
rt.jar...
jsse.jar...
charsets.jar...
localedata.jar...
[root@artisan soft_artisan]#
Step 2 配置 & 刷新 /etc/profile
该配置文件为 全局变量，对所有用户生效 。 也可不配置，在应用中指定JAVA_HOME
[root@artisan java]# vim /etc/profile
[root@artisan java]# /etc/profile 最后 增加
#JDK
export JAVA_HOME=/usr/java/jdk1.8.0_221-amd64
export PATH=$PATH:$JAVA_HOME/bin
export CLASSPATH=.:$JAVA_HOME/jre/lib:$JAVA_HOME/lib:$JAVA_HOME/lib/tools.jar
[root@artisan java]# 刷新 /etc/profile 使其生效
[root@artisan java]# source /etc/profile
[root@artisan java]#
[root@artisan java]#
[root@artisan etc]# java -version
java version "1.8.0_221"
Java(TM) SE Runtime Environment (build 1.8.0_221-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.221-b11, mixed mode)
[root@artisan etc]#
[root@artisan java]# echo $JAVA_HOME
/usr/java/jdk1.8.0_221-amd64
[root@artisan java]# whereis java
java: /usr/bin/java /usr/java/jdk1.8.0_221-amd64/bin/java /usr/share/man/man1/java.1
[root@artisan java]# which java
/usr/bin/java
[root@artisan java]#
安装 tar.gz格式的JDK
#解压到/usr/local/jdk目录下
[root@artisan soft_artisan]# tar -xvzf jdk-8u221-linux-x64.tar.gz -C /usr/local/jdk
[root@artisan ~]# 末尾增加JDK信息
[root@artisan ~]# vim /etc/profile
#JDK
export JAVA_HOME=/usr/local/jdk/jdk1.8.0_221
export PATH=$PATH:$JAVA_HOME/bin
export CLASSPATH=.:$JAVA_HOME/jre/lib:$JAVA_HOME/lib:$JAVA_HOME/lib/tools.jar
[root@artisan ~]# 刷新文件
[root@artisan ~]# source /etc/profile
[root@artisan ~]#
[root@artisan ~]# java -version
java version "1.8.0_221"
Java(TM) SE Runtime Environment (build 1.8.0_221-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.221-b11, mixed mode)
[root@artisan ~]#
[root@artisan ~]# whereis java
java: /usr/local/jdk/jdk1.8.0_221/bin/java
[root@artisan ~]# which java
/usr/local/jdk/jdk1.8.0_221/bin/java
[root@artisan ~]#
多个JDK共存时，设置默认的Java 版本
yum 或者 rpm安装的 JDK，可以使用 alternatives --config java
[root@artisan ~]# alternatives --config java
There is 1 program that provides 'java'.
Selection Command
-----------------------------------------------
*+ 1 /usr/java/jdk1.8.0_221-amd64/jre/bin/java
Enter to keep the current selection[+], or type selection number:
切换默认的JDK信息 ，不过这个时候 /etc/profile 要配置
export JAVA_HOME=/usr/java/default
export PATH=$PATH:$JAVA_HOME/bin
export CLASSPATH=.:$JAVA_HOME/jre/lib:$JAVA_HOME/lib:$JAVA_HOME/lib/tools.jar
看下rpm安装后的jdk目录结构
第二个 jdk1.8.0_221-amd64 是刚才安装Jdk的真实目录，而 latest 则是系统动态切换后指向的最新目录，它链接到了JDK的真实目录。而default文件又链接到 latest，所以 default 就是当前系统默认的JDK目录。 故 变更如上 export JAVA_HOME=/usr/java/default ，记得 source /etc/profile
演示：
[root@artisan soft_artisan]# ll
total 729840
drwxr-xr-x. 7 10 143 4096 Jul 4 19:37 jdk1.8.0_221
drwxr-xr-x. 7 10 143 4096 Oct 5 18:13 jdk1.8.0_231
-rw-r--r--. 1 root root 179505388 Nov 3 02:17 jdk-8u221-linux-x64.rpm
-rw-r--r--. 1 root root 195094741 Nov 3 10:27 jdk-8u221-linux-x64.tar.gz
-rw-r--r--. 1 root root 178589686 Nov 3 02:02 jdk-8u231-linux-x64.rpm
-rw-r--r--. 1 root root 194151339 Nov 3 10:36 jdk-8u231-linux-x64.tar.gz
[root@artisan soft_artisan]# 安装 jdk1.8.221
[root@artisan soft_artisan]# rpm -ivh jdk-8u221-linux-x64.rpm
warning: jdk-8u221-linux-x64.rpm: Header V3 RSA/SHA256 Signature, key ID ec551f03: NOKEY
Preparing... ################################# [100%]
Updating / installing...
1:jdk1.8-2000:1.8.0_221-fcs ################################# [100%]
Unpacking JAR files...
tools.jar...
plugin.jar...
javaws.jar...
deploy.jar...
rt.jar...
jsse.jar...
charsets.jar...
localedata.jar...
[root@artisan soft_artisan]# 查看版本信息
[root@artisan soft_artisan]# java -version
java version "1.8.0_221"
Java(TM) SE Runtime Environment (build 1.8.0_221-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.221-b11, mixed mode)
[root@artisan soft_artisan]#
[root@artisan soft_artisan]# 安装 jdk1.8.231
[root@artisan soft_artisan]# rpm -ivh jdk-8u231-linux-x64.rpm
warning: jdk-8u231-linux-x64.rpm: Header V3 RSA/SHA256 Signature, key ID ec551f03: NOKEY
Preparing... ################################# [100%]
Updating / installing...
1:jdk1.8-2000:1.8.0_231-fcs ################################# [100%]
Unpacking JAR files...
tools.jar...
plugin.jar...
javaws.jar...
deploy.jar...
rt.jar...
jsse.jar...
charsets.jar...
localedata.jar...
[root@artisan soft_artisan]# 查看版本信息
[root@artisan soft_artisan]# java -version
java version "1.8.0_231"
Java(TM) SE Runtime Environment (build 1.8.0_231-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.231-b11, mixed mode)
[root@artisan soft_artisan]#
[root@artisan soft_artisan]#
[root@artisan soft_artisan]# 切换 到 221 （输入1）
[root@artisan soft_artisan]# alternatives --config java
There are 2 programs which provide 'java'.
Selection Command
-----------------------------------------------
1 /usr/java/jdk1.8.0_221-amd64/jre/bin/java
*+ 2 /usr/java/jdk1.8.0_231-amd64/jre/bin/java
Enter to keep the current selection[+], or type selection number: 1
[root@artisan soft_artisan]# 重新查看java -version 已经到了 221
[root@artisan soft_artisan]# java -version
java version "1.8.0_221"
Java(TM) SE Runtime Environment (build 1.8.0_221-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.221-b11, mixed mode)
[root@artisan soft_artisan]#
[root@artisan soft_artisan]#
看下rpm安装的jdk目录 ， dfault 、 lates、真实安装目录
[root@artisan ~]# cd /usr/java/
[root@artisan java]# ll
total 8
lrwxrwxrwx. 1 root root 16 Nov 4 03:54 default -> /usr/java/latest
drwxr-xr-x. 8 root root 4096 Nov 4 03:54 jdk1.8.0_221-amd64
drwxr-xr-x. 8 root root 4096 Nov 4 03:55 jdk1.8.0_231-amd64
lrwxrwxrwx. 1 root root 28 Nov 4 03:55 latest -> /usr/java/jdk1.8.0_231-amd64
[root@artisan java]#
经过验证，似乎不用配置 /etc/profile ，但是仍然对所有用户生效，请看如下验证
[root@artisan java]# useradd test
[root@artisan java]# passwd test
Changing password for user test.
New password:
BAD PASSWORD: The password is shorter than 8 characters
Retype new password:
passwd: all authentication tokens updated successfully.
[root@artisan java]#
[root@artisan java]# su - test
[test@artisan ~]$ java -version
java version "1.8.0_221"
Java(TM) SE Runtime Environment (build 1.8.0_221-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.221-b11, mixed mode)
[test@artisan ~]$
