方法一：手动解压JDK的压缩包，然后设置环境变量

1. 在/usr/目录下创建java目录

[root@localhost ~]# mkdir /usr/java
[root@localhost ~]# cd /usr/java

2.下载jdk，然后解压并copy到/opt/java(任意目录即可)

[root@localhost soft]# tar -xzvf jdk-8u221-linux-x64.tar.gz 
[root@localhost soft]# mkdir /opt/java
[root@localhost soft]# cp -r jdk1.8.0_221/ /opt/java/

3. 设置环境变量，修改/etc/profile，在文件的底部添加如下内容

# set java environment
JAVA_HOME=/opt/java/jdk1.8.0_221
JRE_HOME=/opt/java/jdk1.8.0_221/jre
CLASS_PATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib
PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin
export JAVA_HOME JRE_HOME CLASS_PATH PATH

让修改生效:

[root@localhost java]# source /etc/profile

4.验证JDK有效性

[root@localhost java]# clear
[root@localhost java]# 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@localhost java]# 

方法二：用yum安装JDK

1.查看yum库中都有哪些jdk版本(暂时只发现了openjdk)

[root@localhost java]# yum search java|grep jdk
ldapjdk-javadoc.noarch : Javadoc for ldapjdk
java-1.6.0-openjdk.x86_64 : OpenJDK Runtime Environment
java-1.6.0-openjdk-demo.x86_64 : OpenJDK Demos
java-1.6.0-openjdk-devel.x86_64 : OpenJDK Development Environment
java-1.6.0-openjdk-javadoc.x86_64 : OpenJDK API Documentation
java-1.6.0-openjdk-src.x86_64 : OpenJDK Source Bundle
java-1.7.0-openjdk.x86_64 : OpenJDK Runtime Environment
java-1.7.0-openjdk-accessibility.x86_64 : OpenJDK accessibility connector
java-1.7.0-openjdk-demo.x86_64 : OpenJDK Demos
java-1.7.0-openjdk-devel.x86_64 : OpenJDK Development Environment
java-1.7.0-openjdk-headless.x86_64 : The OpenJDK runtime environment without
java-1.7.0-openjdk-javadoc.noarch : OpenJDK API Documentation
java-1.7.0-openjdk-src.x86_64 : OpenJDK Source Bundle
java-1.8.0-openjdk.i686 : OpenJDK Runtime Environment
java-1.8.0-openjdk.x86_64 : OpenJDK Runtime Environment 8
java-1.8.0-openjdk-accessibility.i686 : OpenJDK accessibility connector
java-1.8.0-openjdk-accessibility.x86_64 : OpenJDK accessibility connector
java-1.8.0-openjdk-accessibility-debug.i686 : OpenJDK accessibility connector
java-1.8.0-openjdk-accessibility-debug.x86_64 : OpenJDK 8 accessibility
java-1.8.0-openjdk-debug.i686 : OpenJDK Runtime Environment with full debug on
java-1.8.0-openjdk-debug.x86_64 : OpenJDK Runtime Environment 8 with full debug
java-1.8.0-openjdk-demo.i686 : OpenJDK Demos
java-1.8.0-openjdk-demo.x86_64 : OpenJDK Demos 8
java-1.8.0-openjdk-demo-debug.i686 : OpenJDK Demos with full debug on
java-1.8.0-openjdk-demo-debug.x86_64 : OpenJDK Demos 8 with full debug on
java-1.8.0-openjdk-devel.i686 : OpenJDK Development Environment
java-1.8.0-openjdk-devel.x86_64 : OpenJDK Development Environment 8
java-1.8.0-openjdk-devel-debug.i686 : OpenJDK Development Environment with full
java-1.8.0-openjdk-devel-debug.x86_64 : OpenJDK Development Environment 8 with
java-1.8.0-openjdk-headless.i686 : OpenJDK Runtime Environment
java-1.8.0-openjdk-headless.x86_64 : OpenJDK Headless Runtime Environment 8
java-1.8.0-openjdk-headless-debug.i686 : OpenJDK Runtime Environment with full
java-1.8.0-openjdk-headless-debug.x86_64 : OpenJDK Runtime Environment with full
java-1.8.0-openjdk-javadoc.noarch : OpenJDK 8 API documentation
java-1.8.0-openjdk-javadoc-debug.noarch : OpenJDK 8 API documentation for
java-1.8.0-openjdk-javadoc-zip.noarch : OpenJDK 8 API documentation compressed
java-1.8.0-openjdk-javadoc-zip-debug.noarch : OpenJDK 8 API documentation
java-1.8.0-openjdk-src.i686 : OpenJDK Source Bundle
java-1.8.0-openjdk-src.x86_64 : OpenJDK Source Bundle 8
java-1.8.0-openjdk-src-debug.i686 : OpenJDK Source Bundle for packages with
java-1.8.0-openjdk-src-debug.x86_64 : OpenJDK Source Bundle 8 for packages with
java-11-openjdk.i686 : OpenJDK Runtime Environment 11
java-11-openjdk.x86_64 : OpenJDK Runtime Environment 11
java-11-openjdk-debug.i686 : OpenJDK Runtime Environment 11 with full debug on
java-11-openjdk-debug.x86_64 : OpenJDK Runtime Environment 11 with full debug on
java-11-openjdk-demo.i686 : OpenJDK Demos 11
java-11-openjdk-demo.x86_64 : OpenJDK Demos 11
java-11-openjdk-demo-debug.i686 : OpenJDK Demos 11 with full debug on
java-11-openjdk-demo-debug.x86_64 : OpenJDK Demos 11 with full debug on
java-11-openjdk-devel.i686 : OpenJDK Development Environment 11
java-11-openjdk-devel.x86_64 : OpenJDK Development Environment 11
java-11-openjdk-devel-debug.i686 : OpenJDK Development Environment 11 with full
java-11-openjdk-devel-debug.x86_64 : OpenJDK Development Environment 11 with
java-11-openjdk-headless.i686 : OpenJDK Headless Runtime Environment 11
java-11-openjdk-headless.x86_64 : OpenJDK Headless Runtime Environment 11
java-11-openjdk-headless-debug.i686 : OpenJDK Runtime Environment with full
java-11-openjdk-headless-debug.x86_64 : OpenJDK Runtime Environment with full
java-11-openjdk-javadoc.i686 : OpenJDK 11 API documentation
java-11-openjdk-javadoc.x86_64 : OpenJDK 11 API documentation
java-11-openjdk-javadoc-debug.i686 : OpenJDK 11 API documentation for packages
java-11-openjdk-javadoc-debug.x86_64 : OpenJDK 11 API documentation for packages
java-11-openjdk-javadoc-zip.i686 : OpenJDK 11 API documentation compressed in
java-11-openjdk-javadoc-zip.x86_64 : OpenJDK 11 API documentation compressed in
java-11-openjdk-javadoc-zip-debug.i686 : OpenJDK 11 API documentation compressed
java-11-openjdk-javadoc-zip-debug.x86_64 : OpenJDK 11 API documentation
java-11-openjdk-jmods.i686 : JMods for OpenJDK 11
java-11-openjdk-jmods.x86_64 : JMods for OpenJDK 11
java-11-openjdk-jmods-debug.i686 : JMods for OpenJDK 11 with full debug on
java-11-openjdk-jmods-debug.x86_64 : JMods for OpenJDK 11 with full debug on
java-11-openjdk-src.i686 : OpenJDK Source Bundle 11
java-11-openjdk-src.x86_64 : OpenJDK Source Bundle 11
java-11-openjdk-src-debug.i686 : OpenJDK Source Bundle for packages with debug
java-11-openjdk-src-debug.x86_64 : OpenJDK Source Bundle 11 for packages with
ldapjdk.noarch : The Mozilla LDAP Java SDK
[root@localhost java]# 

2.选择版本，进行安装，此处选择安装java-1.8.0-openjdk.x86_64

yum install java-1.8.0-openjdk.x86_64

//安装完之后，默认的安装目录是在: /usr/lib/jvm。经验证，该版本在安装后自动设置 环境变量

3.验证(同上一方法)

说明：采用yum方式安装不需要设置环境变量

方法三：用rpm安装JDK

1.下载rpm安装文件
同于现在下载都需要用账号登录，下载步骤略，大家可百度。

2.使用rpm命令安装

[root@localhost soft]# rpm -ivh jdk-8u221-linux-x64.rpm

4.验证(同上一方法)

注:和yum安装类似，不用设置环境变量就可以运行java命令。rpm安装方式默认会把jdk安装到/usr/java/jdk1.8.0_221-amd64，然后通过三层链接，链接到/usr/bin,具体链接如下：

[root@localhost alternatives]# cd /usr/java/
[root@localhost java]# ll
total 4
lrwxrwxrwx. 1 root root   16 Aug 17 21:26 default -> /usr/java/latest
drwxr-xr-x. 8 root root 4096 Aug 17 21:26 jdk1.8.0_221-amd64
lrwxrwxrwx. 1 root root   28 Aug 17 21:26 latest -> /usr/java/jdk1.8.0_221-amd64
[root@localhost java]# 
[root@localhost java]# cd /bin/
[root@localhost bin]# ll |grep java
lrwxrwxrwx. 1 root root        22 Aug 17 21:26 java -> /etc/alternatives/java
lrwxrwxrwx. 1 root root        23 Aug 17 21:26 javac -> /etc/alternatives/javac
lrwxrwxrwx. 1 root root        25 Aug 17 21:26 javadoc -> /etc/alternatives/javadoc
lrwxrwxrwx. 1 root root        32 Aug 17 21:26 javafxpackager -> /etc/alternatives/javafxpackager
lrwxrwxrwx. 1 root root        23 Aug 17 21:26 javah -> /etc/alternatives/javah
lrwxrwxrwx. 1 root root        23 Aug 17 21:26 javap -> /etc/alternatives/javap
lrwxrwxrwx. 1 root root        30 Aug 17 21:26 javapackager -> /etc/alternatives/javapackager
lrwxrwxrwx. 1 root root        30 Aug 17 21:26 java-rmi.cgi -> /etc/alternatives/java-rmi.cgi
lrwxrwxrwx. 1 root root        24 Aug 17 21:26 javaws -> /etc/alternatives/javaws
[root@localhost bin]#